feat: list_bases returns registered table storage prefixes

Return the additional storage bases for the current table snapshot
on native, memory, namespace, and Cloud clients.

.bumpversion.toml

@@ -1,5 +1,5 @@
 [tool.bumpversion]
-current_version = "0.37.1-beta.0"
+current_version = "0.38.0-beta.0"
 parse = """(?x)
     (?P<major>0|[1-9]\\d*)\\.
     (?P<minor>0|[1-9]\\d*)\\.

.github/workflows/codex-update-lance-dependency.yml

@@ -4,14 +4,14 @@ on:
   workflow_call:
     inputs:
       tag:
-        description: "Tag name from Lance. If omitted, the skill will use the latest Lance release that needs an update."
+        description: "Tag name from Lance (e.g. `v7.2.0-beta.1`). If omitted, the newest release is resolved automatically — stable releases are preferred over pre-releases — and the run is skipped if it is not newer than the version currently pinned in Cargo.toml."
         required: false
         default: ""
         type: string
   workflow_dispatch:
     inputs:
       tag:
-        description: "Tag name from Lance. Leave empty to use the latest Lance release that needs an update."
+        description: "Tag name from Lance (e.g. `v7.2.0-beta.1`). Leave empty to resolve the newest release automatically — stable releases are preferred over pre-releases — and skip the run if it is not newer than the version currently pinned in Cargo.toml."
         required: false
         default: ""
         type: string

.github/workflows/docs-link-check.yml

@@ -0,0 +1,243 @@
+name: Check doc links
+
+# Checking external links is inherently noisy: third-party sites rate-limit
+# automated clients, reject non-browser user agents, and go down temporarily.
+# Blocking pull requests on that trades a lot of false failures for very little
+# signal, so this runs on a schedule and reports findings in a single tracking
+# issue instead of failing anyone's build.
+on:
+  schedule:
+    - cron: "0 7 * * *"
+  workflow_dispatch:
+
+# The report lives in one repository-global issue, so runs must not overlap: a
+# lookup racing a create produces duplicate issues, and a healthy run closing
+# the issue while a failing run only rewrites its body would leave a broken
+# report closed. The group is deliberately ref-independent so that a manual
+# dispatch serializes against the scheduled run.
+concurrency:
+  group: docs-link-check
+  cancel-in-progress: false
+
+permissions: {}
+
+env:
+  REPORT_TITLE: "Docs link checker report"
+
+jobs:
+  scan:
+    name: Scan links
+    runs-on: ubuntu-24.04
+    # lychee-action is pinned by SHA, but its wrapper downloads the lychee
+    # release tarball at run time without verifying a digest, and hands the
+    # resulting binary a GitHub token. Release assets remain replaceable, so
+    # that binary is confined to a job whose token can only read public
+    # content; everything that writes runs in the report job below.
+    permissions:
+      contents: read
+    outputs:
+      checker_outcome: ${{ steps.lychee.outcome }}
+      exit_code: ${{ steps.lychee.outputs.exit_code }}
+      status: ${{ steps.validate.outputs.status }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+        with:
+          # workflow_dispatch can run from any ref, but the report is
+          # repository-global. Always measure the default branch so a manual
+          # run from a topic branch cannot close a report that main warrants,
+          # or overwrite it with branch-only findings.
+          ref: ${{ github.event.repository.default_branch }}
+          persist-credentials: false
+
+      - name: Check links
+        id: lychee
+        continue-on-error: true
+        uses: lycheeverse/lychee-action@e7477775783ea5526144ba13e8db5eec57747ce8 # v2.9.0
+        with:
+          # Restricted to http(s) on purpose. Much of docs/src is generated
+          # API reference (the js/ tree comes from `npm run docs` in nodejs)
+          # and the hand-written pages use mkdocstrings cross-references and
+          # nav-relative paths that only resolve in the site mkdocs builds,
+          # not in this checkout, so relative links would be reported as
+          # broken on every run.
+          args: >-
+            --scheme https
+            --scheme http
+            --no-progress
+            --max-retries 3
+            --timeout 20
+            'docs/src/**/*.md'
+          format: json
+          output: ./lychee/out.json
+          jobSummary: false
+          # The report issue, not a red workflow run, is the signal for link
+          # findings and checker failures alike.
+          fail: false
+
+      - name: Validate report
+        id: validate
+        # lychee does not reserve exit code 2 for broken links: its CLI
+        # parser also exits 2 on an invalid option, before any link was
+        # checked or any report written. Only a parseable report whose
+        # counts agree with a completed exit code (0 or 2) counts as a link
+        # verdict. Everything else becomes a checker-error report instead of
+        # failing the workflow. Exit 2 covers timeouts as well as errors, and a
+        # timed-out host is exactly the transient unavailability this report
+        # exists to surface, so both count as findings. Requiring total > 0
+        # also catches a glob that silently stopped matching any file.
+        if: always()
+        env:
+          CHECKER_OUTCOME: ${{ steps.lychee.outcome }}
+          EXIT_CODE: ${{ steps.lychee.outputs.exit_code }}
+        run: |
+          status=checker-error
+          if [[ "$CHECKER_OUTCOME" == success ]] &&
+             [[ "$EXIT_CODE" == 0 || "$EXIT_CODE" == 2 ]] &&
+             jq -e --argjson code "$EXIT_CODE" '
+               (.total > 0) and
+               (if $code == 0
+                then .errors == 0 and .timeouts == 0
+                  and (.error_map | length == 0) and (.timeout_map | length == 0)
+                else (.errors + .timeouts) > 0
+                  and ((.error_map | length) + (.timeout_map | length)) > 0
+                end)
+             ' ./lychee/out.json
+          then
+            if [[ "$EXIT_CODE" == 0 ]]; then
+              status=healthy
+            else
+              status=findings
+            fi
+          fi
+          echo "status=$status" >> "$GITHUB_OUTPUT"
+          echo "Validated link check as $status"
+
+      - name: Upload report
+        if: steps.validate.outputs.status == 'findings'
+        uses: actions/upload-artifact@v7
+        with:
+          name: link-report
+          path: ./lychee/out.json
+          retention-days: 7
+
+  report:
+    name: Update report issue
+    needs: scan
+    runs-on: ubuntu-24.04
+    # Deliberately no checkout: this job needs the report artifact and the
+    # issues API, not the repository contents.
+    permissions:
+      issues: write
+    env:
+      CHECKER_OUTCOME: ${{ needs.scan.outputs.checker_outcome }}
+      EXIT_CODE: ${{ needs.scan.outputs.exit_code }}
+      STATUS: ${{ needs.scan.outputs.status }}
+      GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+    steps:
+      - name: Find existing report issue
+        id: report
+        # Matched on title alone, and through search rather than a listing:
+        # the issue action applies labels in a separate call after creating the
+        # issue, so a label filter misses a half-created report, and this
+        # repository has far more open issues than one listing page holds.
+        # Closed issues are included because a healthy run closes the report:
+        # an open-only lookup would forget that identity and the next failing
+        # run would open a duplicate. The oldest match stays the canonical
+        # report and is reopened below when a problem recurs.
+        run: |
+          match=$(gh issue list --repo "$GITHUB_REPOSITORY" --state all \
+            --search "in:title \"$REPORT_TITLE\" author:app/github-actions" \
+            --limit 50 --json number,title,state \
+            --jq "[.[] | select(.title == \"$REPORT_TITLE\")] | sort_by(.number) | first // empty")
+          echo "number=$(jq -r '.number // empty' <<<"$match")" >> "$GITHUB_OUTPUT"
+          echo "state=$(jq -r '.state // empty' <<<"$match")" >> "$GITHUB_OUTPUT"
+
+      - name: Download report
+        if: env.STATUS == 'findings'
+        uses: actions/download-artifact@v8
+        with:
+          name: link-report
+          path: ./lychee
+
+      - name: Compose report
+        if: env.STATUS == 'findings'
+        run: |
+          run_url="$GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID"
+          {
+            echo "Broken documentation links found by [\`$GITHUB_WORKFLOW\`]($run_url)."
+            echo
+            echo "This issue is rewritten by every scheduled run and closed automatically once all links resolve."
+            echo
+            echo "Entries can be false positives: some sites rate-limit or block automated clients while working fine in a browser. Confirm before editing the docs, and add persistent offenders to \`--exclude\` in \`.github/workflows/docs-link-check.yml\`."
+            echo
+            # Timeouts are reported alongside errors: entries land in
+            # timeout_map with a status text instead of an HTTP code.
+            jq -r '
+              "\(.errors) of \(.total) links failed, \(.timeouts) timed out.",
+              "",
+              ([(.error_map | to_entries[]), (.timeout_map | to_entries[])]
+               | group_by(.key)[] |
+                "### Errors in \(.[0].key)",
+                "",
+                (map(.value[])[] | "* [\(.status.code // .status.text // "ERR")] <\(.url)> — \(.status.details // .status.text // "unknown error")"),
+                "")
+            ' ./lychee/out.json
+          } > ./lychee/issue.md
+
+      - name: Compose checker error report
+        if: env.STATUS == 'checker-error'
+        run: |
+          mkdir -p ./lychee
+          run_url="$GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID"
+          {
+            echo "The documentation link check did not complete in [the latest run]($run_url)."
+            echo
+            echo "This issue is rewritten by every scheduled run and closed automatically once a trustworthy run finds that all links resolve."
+            echo
+            echo "The checker did not produce a trustworthy link verdict. Treat the previous result, if any, as stale until a later run completes."
+            echo
+            echo "* Action outcome: \`$CHECKER_OUTCOME\`"
+            echo "* Exit code: \`${EXIT_CODE:-not reported}\`"
+            echo "* Verdict validation: \`failed\`"
+          } > ./lychee/issue.md
+
+      - name: Reopen report issue
+        # A healthy run closes the report, and the issue action below only
+        # rewrites the body of whatever number it is given. Without an
+        # explicit reopen, a later finding or checker error would rewrite a
+        # closed issue. A CLOSED state implies the lookup found a canonical
+        # issue, so no separate emptiness check.
+        if: >-
+          env.STATUS != 'healthy' &&
+          steps.report.outputs.state == 'CLOSED'
+        env:
+          ISSUE_NUMBER: ${{ steps.report.outputs.number }}
+        run: |
+          run_url="$GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID"
+          gh issue reopen "$ISSUE_NUMBER" --repo "$GITHUB_REPOSITORY" \
+            --comment "The documentation link checker reported a problem again in [the latest run]($run_url)."
+
+      - name: Report link-check problem
+        if: env.STATUS != 'healthy'
+        uses: peter-evans/create-issue-from-file@fca9117c27cdc29c6c4db3b86c48e4115a786710 # v6.0.0
+        with:
+          # Empty on the first failing run, which creates the issue; afterwards
+          # the same issue is updated in place.
+          issue-number: ${{ steps.report.outputs.number }}
+          title: ${{ env.REPORT_TITLE }}
+          content-filepath: ./lychee/issue.md
+          labels: documentation
+
+      - name: Close report issue once links are healthy
+        # An OPEN state implies the lookup found a canonical issue; a report
+        # that is already closed needs nothing.
+        if: >-
+          env.STATUS == 'healthy' &&
+          steps.report.outputs.state == 'OPEN'
+        env:
+          ISSUE_NUMBER: ${{ steps.report.outputs.number }}
+        run: |
+          run_url="$GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID"
+          gh issue close "$ISSUE_NUMBER" --repo "$GITHUB_REPOSITORY" \
+            --comment "All documentation links resolved in [the latest run]($run_url)."

.github/workflows/pypi-publish.yml

@@ -69,6 +69,16 @@ jobs:
         uses: actions/setup-python@v6
         with:
           python-version: "3.10"
+      - name: Add swap for Arm fat LTO
+        if: matrix.config.platform == 'aarch64'
+        shell: bash
+        run: |
+          swap_file="$RUNNER_TEMP/lancedb-swap"
+          sudo fallocate --length 16G "$swap_file"
+          sudo chmod 600 "$swap_file"
+          sudo mkswap "$swap_file"
+          sudo swapon "$swap_file"
+          free -h
       - uses: ./.github/workflows/build_linux_wheel
         with:
           python-minor-version: 10

.github/workflows/rust.yml

@@ -296,16 +296,18 @@ jobs:
           cargo update -p aws-types --precise 1.3.9
           cargo update -p aws-sigv4 --precise 1.3.5
           cargo update -p aws-credential-types --precise 1.2.8
-          cargo update -p aws-smithy-checksums --precise 0.63.9
+          # aws-smithy-checksums must stay at or above 0.63.13: OpenDAL's S3
+          # service needs crc-fast ~1.9, and older releases pin it to ~1.3.
+          cargo update -p aws-smithy-checksums --precise 0.63.13
           cargo update -p aws-smithy-runtime --precise 1.9.3
-          cargo update -p aws-smithy-http --precise 0.62.4
-          cargo update -p aws-smithy-eventstream --precise 0.60.12
+          cargo update -p aws-smithy-http --precise 0.62.6
+          cargo update -p aws-smithy-eventstream --precise 0.60.14
           cargo update -p aws-smithy-http-client --precise 1.1.3
           cargo update -p aws-smithy-observability --precise 0.1.4
           cargo update -p aws-smithy-query --precise 0.60.8
-          cargo update -p aws-smithy-runtime-api --precise 1.9.1
-          cargo update -p aws-smithy-async --precise 1.2.6
-          cargo update -p aws-smithy-types --precise 1.3.5
+          cargo update -p aws-smithy-runtime-api --precise 1.9.3
+          cargo update -p aws-smithy-async --precise 1.2.7
+          cargo update -p aws-smithy-types --precise 1.3.6
           cargo update -p aws-smithy-xml --precise 0.60.11
           cargo update -p home --precise 0.5.9
       - name: cargo +${{ matrix.msrv }} check

Cargo.toml

@@ -13,20 +13,20 @@ categories = ["database-implementations"]
 rust-version = "1.91.0"
 
 [workspace.dependencies]
-lance = { "version" = "=10.1.0-beta.1", default-features = false, "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-core = { "version" = "=10.1.0-beta.1", "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-datagen = { "version" = "=10.1.0-beta.1", "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-file = { "version" = "=10.1.0-beta.1", "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-io = { "version" = "=10.1.0-beta.1", default-features = false, "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-index = { "version" = "=10.1.0-beta.1", "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-linalg = { "version" = "=10.1.0-beta.1", "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-namespace = { "version" = "=10.1.0-beta.1", "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-namespace-impls = { "version" = "=10.1.0-beta.1", default-features = false, "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-table = { "version" = "=10.1.0-beta.1", "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-testing = { "version" = "=10.1.0-beta.1", "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-datafusion = { "version" = "=10.1.0-beta.1", "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-encoding = { "version" = "=10.1.0-beta.1", "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
-lance-arrow = { "version" = "=10.1.0-beta.1", "tag" = "v10.1.0-beta.1", "git" = "https://github.com/lance-format/lance.git" }
+lance = { "version" = "=11.0.0-beta.13", default-features = false, "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-core = { "version" = "=11.0.0-beta.13", "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-datagen = { "version" = "=11.0.0-beta.13", "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-file = { "version" = "=11.0.0-beta.13", "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-io = { "version" = "=11.0.0-beta.13", default-features = false, "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-index = { "version" = "=11.0.0-beta.13", "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-linalg = { "version" = "=11.0.0-beta.13", "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-namespace = { "version" = "=11.0.0-beta.13", "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-namespace-impls = { "version" = "=11.0.0-beta.13", default-features = false, "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-table = { "version" = "=11.0.0-beta.13", "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-testing = { "version" = "=11.0.0-beta.13", "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-datafusion = { "version" = "=11.0.0-beta.13", "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-encoding = { "version" = "=11.0.0-beta.13", "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
+lance-arrow = { "version" = "=11.0.0-beta.13", "tag" = "v11.0.0-beta.13", "git" = "https://github.com/lance-format/lance.git" }
 ahash = "0.8"
 # Note that this one does not include pyarrow
 arrow = { version = "58.0.0", optional = false }
@@ -52,7 +52,7 @@ env_logger = "0.11"
 half = { "version" = "2.7.1", default-features = false, features = [
     "num-traits",
 ] }
-futures = "0"
+futures = "0.3"
 log = "0.4"
 metrics = "0.24"
 metrics-util = "0.19"

deny.toml

@@ -101,6 +101,13 @@ ignore = [
     # https://rustsec.org/advisories/RUSTSEC-2026-0195
     { id = "RUSTSEC-2026-0194", reason = "transitive via inferno/lance/opendal; XML from trusted cloud endpoints, not attacker-controlled" },
     { id = "RUSTSEC-2026-0195", reason = "transitive via inferno/lance/opendal; XML from trusted cloud endpoints, not attacker-controlled" },
+    # smartstring: unmaintained — the repository was archived by its author on
+    # 2026-05-03. Not a vulnerability. Reached only transitively through polars
+    # (polars-core/-io/-ops/-time/-utils); nothing in LanceDB depends on it directly.
+    # The advisory states no safe upgrade is available: upstream recommends
+    # compact_str/smol_str, so clearing this requires polars to migrate.
+    # https://rustsec.org/advisories/RUSTSEC-2026-0249
+    { id = "RUSTSEC-2026-0249", reason = "smartstring unmaintained via polars; no fixed upstream release" },
 ]
 
 # ---------------------------------------------------------------------------

docs/src/java/java.md

@@ -14,7 +14,7 @@ Add the following dependency to your `pom.xml`:
 <dependency>
     <groupId>com.lancedb</groupId>
     <artifactId>lancedb-core</artifactId>
-    <version>0.37.1-beta.0</version>
+    <version>0.38.0-beta.0</version>
 </dependency>
 ```
 

docs/src/js/classes/Connection.md

@@ -386,6 +386,29 @@ Drop an existing table.
 
 ***
 
+### dropTableAsync()
+
+```ts
+abstract dropTableAsync(name, namespacePath?): Promise<Job>
+```
+
+Start dropping a table and return its cleanup job.
+
+The table may become unavailable before its data files are removed. Wait
+on the returned job to know when cleanup has finished.
+
+#### Parameters
+
+* **name**: `string`
+
+* **namespacePath?**: `string`[]
+
+#### Returns
+
+`Promise`&lt;[`Job`](Job.md)&gt;
+
+***
+
 ### getJob()
 
 ```ts

docs/src/js/classes/Table.md

@@ -69,14 +69,34 @@ abstract addColumns(newColumnTransforms): Promise<AddColumnsResult>
 
 Add new columns with defined values.
 
+The `{ computed }` form stores the expression rather than evaluating it
+now: the column is committed with no values, and rows get them from
+[Table#refreshColumn](Table.md#refreshcolumn). Declaring one therefore costs the same on a
+large table as on an empty one.
+
+A refresh does not revisit rows it has already filled, so mutating an
+input leaves the value computed at fill time; recomputing means dropping
+the column and declaring it again. While a declaration reads a column,
+that column cannot be renamed, retyped or dropped.
+
+On LanceDB Cloud and Enterprise the expression is planned by the
+server, and the refresh runs as a server job -- see
+[Table#refreshColumnAsync](Table.md#refreshcolumnasync).
+
 #### Parameters
 
-* **newColumnTransforms**: `Field`&lt;`any`&gt; \| `Field`&lt;`any`&gt;[] \| `Schema`&lt;`any`&gt; \| [`AddColumnsSql`](../interfaces/AddColumnsSql.md)[]
+* **newColumnTransforms**:
+    \| `Field`&lt;`any`&gt;
+    \| `Field`&lt;`any`&gt;[]
+    \| `Schema`&lt;`any`&gt;
+    \| [`AddColumnsSql`](../interfaces/AddColumnsSql.md)[]
+    \| `object`
     Either:
     - An array of objects with column names and SQL expressions to calculate values
     - A single Arrow Field defining one column with its data type (column will be initialized with null values)
     - An array of Arrow Fields defining columns with their data types (columns will be initialized with null values)
     - An Arrow Schema defining columns with their data types (columns will be initialized with null values)
+    - `{ computed }`, declaring columns defined by a SQL expression whose type and inputs are derived from it
 
 #### Returns
 
@@ -85,6 +105,13 @@ Add new columns with defined values.
 A promise that resolves to an object
 containing the new version number of the table after adding the columns.
 
+#### Example
+
+```ts
+await table.addColumns({ computed: [{ name: "doubled", valueSql: "x * 2" }] });
+const { rowsFilled } = await table.refreshColumn("doubled");
+```
+
 ***
 
 ### alterColumns()
@@ -431,9 +458,10 @@ Read the [LsmWriteSpec](../interfaces/LsmWriteSpec.md) currently installed on th
 
 Resolves to `undefined` when the MemWAL LSM write path is not enabled (no
 spec has been set, or it was removed with [Table#unsetLsmWriteSpec](Table.md#unsetlsmwritespec)).
-The returned spec — including its `maintainedIndexes` and
-`writerConfigDefaults` — mirrors what was passed to
-[Table#setLsmWriteSpec](Table.md#setlsmwritespec).
+The returned spec mirrors what was passed to
+[Table#setLsmWriteSpec](Table.md#setlsmwritespec), except that `maintainedIndexes` always
+reports the concrete list resolved when the spec was set — `undefined`
+never round-trips.
 
 #### Returns
 
@@ -717,6 +745,67 @@ for await (const batch of table.query()) {
 
 ***
 
+### refreshColumn()
+
+```ts
+abstract refreshColumn(column): Promise<RefreshColumnResult>
+```
+
+Fill the rows of a computed column that hold no value yet.
+
+Rows appended since the last refresh are filled by the next one; rows
+already filled are left as they are, so the call is idempotent and does
+not observe a mutated input. Local tables only: a remote refresh runs
+as a server job, through [Table#refreshColumnAsync](Table.md#refreshcolumnasync).
+
+#### Parameters
+
+* **column**: `string`
+    The name of the computed column to fill.
+
+#### Returns
+
+`Promise`&lt;[`RefreshColumnResult`](../interfaces/RefreshColumnResult.md)&gt;
+
+A promise that resolves to the
+number of rows filled and the new version number of the table.
+
+***
+
+### refreshColumnAsync()
+
+```ts
+abstract refreshColumnAsync(column): Promise<Job>
+```
+
+Like [Table#refreshColumn](Table.md#refreshcolumn), but returns a handle to the refresh
+job instead of blocking until it completes.
+
+The job may already be complete when returned; callers must not assume
+the column is filled until [Job.wait](Job.md#wait) resolves. Invalid input --
+an unknown column, or one that is not computed -- rejects here rather
+than failing the job. On local tables the job runs in-process; on
+LanceDB Cloud and Enterprise it is the server's backfill job.
+
+#### Parameters
+
+* **column**: `string`
+    The name of the computed column to fill.
+
+#### Returns
+
+`Promise`&lt;[`Job`](Job.md)&gt;
+
+#### Example
+
+```ts
+const job = await table.refreshColumnAsync("doubled");
+await job.wait();
+console.log(await job.status()); // "finished"
+```
+
+***
+
 ### restore()
 
 ```ts
@@ -806,6 +895,11 @@ All variants require the table to have an unenforced primary key
 ([Table#setUnenforcedPrimaryKey](Table.md#setunenforcedprimarykey)); bucket sharding additionally
 requires it to be the single column being bucketed.
 
+Omitting `maintainedIndexes` maintains every index on the table, resolved
+here, failing if one cannot be maintained — name them to install anyway.
+Naming them pins an exact set, and a still-building index is rejected
+rather than quietly omitted.
+
 #### Parameters
 
 * **spec**: [`LsmWriteSpec`](../interfaces/LsmWriteSpec.md)

docs/src/js/globals.md

@@ -105,6 +105,7 @@
 - [OptimizeOptions](interfaces/OptimizeOptions.md)
 - [OptimizeStats](interfaces/OptimizeStats.md)
 - [QueryExecutionOptions](interfaces/QueryExecutionOptions.md)
+- [RefreshColumnResult](interfaces/RefreshColumnResult.md)
 - [RemovalStats](interfaces/RemovalStats.md)
 - [RenameTableOptions](interfaces/RenameTableOptions.md)
 - [RestNamespaceConfig](interfaces/RestNamespaceConfig.md)

docs/src/js/interfaces/LsmWriteSpec.md

@@ -34,7 +34,9 @@ Bucket and identity variants: the sharding column.
 optional maintainedIndexes: string[];
 ```
 
-Names of indexes the MemWAL should keep up to date during writes.
+Indexes the MemWAL keeps up to date. Omit to maintain every supported
+index, resolved on install — a snapshot, so indexes created later are not
+maintained. Pass `[]` for none.
 
 ***
 

docs/src/js/interfaces/RefreshColumnResult.md

@@ -0,0 +1,23 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / RefreshColumnResult
+
+# Interface: RefreshColumnResult
+
+## Properties
+
+### rowsFilled
+
+```ts
+rowsFilled: number;
+```
+
+***
+
+### version
+
+```ts
+version: number;
+```

docs/src/js/interfaces/TableStatistics.md

@@ -44,4 +44,7 @@ The number of rows in the table
 totalBytes: number;
 ```
 
-The total number of bytes in the table
+The total size, in bytes, of the table's data files, index files, and
+overlay files
+
+Read from the manifest, so this excludes deletion files and manifests.

docs/src/python/python.md

@@ -31,7 +31,7 @@ is also an [asynchronous API client](#connections-asynchronous).
 ## Namespaces (Synchronous)
 
 A namespace-backed connection resolves tables through a
-[Lance namespace](https://lancedb.github.io/lance-namespace/) service instead of
+[Lance namespace](https://lance-format.github.io/lance-namespace/) service instead of
 listing a storage directory.
 
 ::: lancedb.connect_namespace

java/lancedb-core/pom.xml

@@ -8,7 +8,7 @@
     <parent>
       <groupId>com.lancedb</groupId>
       <artifactId>lancedb-parent</artifactId>
-      <version>0.37.1-beta.0</version>
+      <version>0.38.0-beta.0</version>
       <relativePath>../pom.xml</relativePath>
     </parent>
 

java/pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>com.lancedb</groupId>
     <artifactId>lancedb-parent</artifactId>
-    <version>0.37.1-beta.0</version>
+    <version>0.38.0-beta.0</version>
     <packaging>pom</packaging>
     <name>${project.artifactId}</name>
     <description>LanceDB Java SDK Parent POM</description>
@@ -28,7 +28,7 @@
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <arrow.version>15.0.0</arrow.version>
-        <lance-core.version>10.1.0-beta.1</lance-core.version>
+        <lance-core.version>11.0.0-beta.13</lance-core.version>
         <spotless.skip>false</spotless.skip>
         <spotless.version>2.30.0</spotless.version>
         <spotless.java.googlejavaformat.version>1.7</spotless.java.googlejavaformat.version>

nodejs/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "lancedb-nodejs"
 edition.workspace = true
-version = "0.37.1-beta.0"
+version = "0.38.0-beta.0"
 publish = false
 license.workspace = true
 description.workspace = true

nodejs/__test__/arrow.test.ts

@@ -6,7 +6,9 @@ import * as arrow17 from "apache-arrow-17";
 import * as arrow18 from "apache-arrow-18";
 
 import {
+  Vector as CurrentVector,
   convertToTable,
+  tableFromIPC as currentTableFromIPC,
   fromBufferToRecordBatch,
   fromDataToBuffer,
   fromRecordBatchToBuffer,
@@ -19,6 +21,7 @@ import {
   FunctionOptions,
 } from "../lancedb/embedding/embedding_function";
 import { EmbeddingFunctionConfig } from "../lancedb/embedding/registry";
+import { sanitizeTable } from "../lancedb/sanitize";
 
 // biome-ignore lint/suspicious/noExplicitAny: skip
 function sampleRecords(): Array<Record<string, any>> {
@@ -64,7 +67,11 @@ describe.each([arrow15, arrow16, arrow17, arrow18])(
       tableFromIPC,
       DataType,
       Dictionary,
+      RecordBatch: ArrowRecordBatch,
+      Table: ArrowTable,
       Uint8: ArrowUint8,
+      makeData: arrowMakeData,
+      vectorFromArray,
       // biome-ignore lint/suspicious/noExplicitAny: <explanation>
     } = <any>arrow;
     type Schema = ApacheArrow["Schema"];
@@ -1054,6 +1061,114 @@ describe.each([arrow15, arrow16, arrow17, arrow18])(
     });
 
     describe("when using two versions of arrow", function () {
+      it("preserves a dictionary shared by multiple fields", async function () {
+        const values = ["alpha", "beta", "alpha"];
+        const dictionaryVector = vectorFromArray(values);
+        const batch = new ArrowRecordBatch({
+          first: dictionaryVector.data[0],
+          second: dictionaryVector.data[0],
+        });
+        const table = new ArrowTable([batch]);
+
+        const sanitized = sanitizeTable(table);
+        expect([...sanitized.getChild("first")!]).toEqual(values);
+        expect([...sanitized.getChild("second")!]).toEqual(values);
+        const firstType = sanitized.schema.fields[0].type as {
+          dictionary: unknown;
+        };
+        const secondType = sanitized.schema.fields[1].type as {
+          dictionary: unknown;
+        };
+        expect(secondType.dictionary).toBe(firstType.dictionary);
+        expect(sanitized.batches[0].data.children[1].dictionary).toBe(
+          sanitized.batches[0].data.children[0].dictionary,
+        );
+
+        const buf = await fromDataToBuffer(table);
+        const actual = currentTableFromIPC(buf);
+        expect([...actual.getChild("first")!]).toEqual(values);
+        expect([...actual.getChild("second")!]).toEqual(values);
+      });
+
+      it("preserves shared dictionary data from another Arrow version", async function () {
+        const values = ["alpha", "beta", "alpha"];
+        const dictionaryVector = vectorFromArray(values);
+        const firstBatch = new ArrowRecordBatch({
+          label: dictionaryVector.slice(0, 2).data[0],
+        });
+        const secondBatch = new ArrowRecordBatch({
+          label: dictionaryVector.slice(2).data[0],
+        });
+        const table = new ArrowTable([firstBatch, secondBatch]);
+
+        const sanitized = sanitizeTable(table);
+        expect([...sanitized.getChild("label")!]).toEqual(values);
+
+        const dictionaries = sanitized.batches.map(
+          (batch) => batch.data.children[0].dictionary,
+        );
+        expect(dictionaries[0]).toBeInstanceOf(CurrentVector);
+        expect(dictionaries[1]).toBe(dictionaries[0]);
+
+        const buf = await fromDataToBuffer(table);
+        const actual = currentTableFromIPC(buf);
+        expect([...actual.getChild("label")!]).toEqual(values);
+      });
+
+      it("preserves shared chunks in growing dictionaries", async function () {
+        const type = new Dictionary(new Utf8(), new Int32(), 42, false);
+        const firstDictionary = vectorFromArray(["alpha", "beta"], new Utf8());
+        const secondDictionary = firstDictionary.concat(
+          vectorFromArray(["gamma"], new Utf8()),
+        );
+        const firstData = arrowMakeData({
+          type,
+          data: Int32Array.from([0, 1]),
+          dictionary: firstDictionary,
+        });
+        const secondData = arrowMakeData({
+          type,
+          data: Int32Array.from([2]),
+          dictionary: secondDictionary,
+        });
+        const table = new ArrowTable([
+          new ArrowRecordBatch({ label: firstData }),
+          new ArrowRecordBatch({ label: secondData }),
+        ]);
+
+        const sanitized = sanitizeTable(table);
+        const expected = ["alpha", "beta", "gamma"];
+        expect([...sanitized.getChild("label")!]).toEqual(expected);
+        const firstLocalDictionary =
+          sanitized.batches[0].data.children[0].dictionary!;
+        const secondLocalDictionary =
+          sanitized.batches[1].data.children[0].dictionary!;
+        expect(secondLocalDictionary.data[0]).toBe(
+          firstLocalDictionary.data[0],
+        );
+
+        const buf = await fromTableToBuffer(sanitized);
+        const actual = currentTableFromIPC(buf);
+        expect([...actual.getChild("label")!]).toEqual(expected);
+      });
+
+      it("can serialize list data from another Arrow version", async function () {
+        const values = [["anime", "action"], [], null];
+        const vector = vectorFromArray(
+          values,
+          new List(new Field("item", new Utf8(), true)),
+        );
+        const table = new ArrowTable({ tags: vector });
+
+        const buf = await fromDataToBuffer(table);
+        const actual = currentTableFromIPC(buf);
+        const actualTags = actual.getChild("tags");
+
+        expect(actualTags?.get(0)?.toJSON()).toEqual(values[0]);
+        expect(actualTags?.get(1)?.toJSON()).toEqual(values[1]);
+        expect(actualTags?.get(2)).toBeNull();
+      });
+
       it("can still import data", async function () {
         const schema = new arrow15.Schema([
           new arrow15.Field("id", new arrow15.Int32()),

nodejs/__test__/connection.test.ts

@@ -89,6 +89,16 @@ describe("given a connection", () => {
     await db.createTable("test4", [{ id: 1 }, { id: 2 }]);
   });
 
+  it("should return a completed job when dropping a local table", async () => {
+    await db.createTable("async-drop", [{ id: 1 }]);
+
+    const job = await db.dropTableAsync("async-drop");
+    expect(job.id).toBeNull();
+    await expect(job.status()).resolves.toBe("finished");
+    await job.wait();
+    await expect(db.tableNames()).resolves.toEqual([]);
+  });
+
   it("should fail if creating table twice, unless overwrite is true", async () => {
     let tbl = await db.createTable("test", [{ id: 1 }, { id: 2 }]);
     await expect(tbl.countRows()).resolves.toBe(2);

nodejs/__test__/embedding.test.ts

@@ -11,8 +11,11 @@ import {
   Float16,
   Float32,
   Float64,
+  Int32,
   Schema,
   Utf8,
+  fromDataToBuffer,
+  tableFromIPC,
 } from "../lancedb/arrow";
 import { EmbeddingFunction, LanceSchema } from "../lancedb/embedding";
 import { getRegistry, register } from "../lancedb/embedding/registry";
@@ -184,6 +187,63 @@ describe("embedding functions", () => {
     const vector0 = JSON.parse(JSON.stringify(arr[0].vector));
     expect(vector0).toEqual([1, 2, 3]);
   });
+
+  it("should append generated vectors to a non-nullable schema", async () => {
+    @register("non_nullable_schema_test")
+    class MockEmbeddingFunction extends EmbeddingFunction<string> {
+      ndims() {
+        return 3;
+      }
+      embeddingDataType(): Float {
+        return new Float64();
+      }
+      async computeSourceEmbeddings(data: string[]) {
+        return data.map(() => [1, 2, 3]);
+      }
+    }
+
+    const schema = new Schema([
+      new Field("id", new Int32()),
+      new Field("text", new Utf8()),
+      new Field("type", new Utf8()),
+      new Field(
+        "vector",
+        new FixedSizeList(3, new Field("item", new Float64())),
+      ),
+    ]);
+    const func = new MockEmbeddingFunction();
+    const db = await connect(tmpDir.name);
+    const table = await db.createEmptyTable("test_non_nullable", schema, {
+      embeddingFunction: {
+        function: func,
+        sourceColumn: "text",
+      },
+    });
+
+    const data = [
+      { id: 1, text: "Carrot", type: "vegetable" },
+      { id: 2, text: "Apple", type: "fruit" },
+    ];
+    const buffer = await fromDataToBuffer(
+      data,
+      undefined,
+      await table.schema(),
+    );
+    const generatedTable = tableFromIPC(buffer);
+    const vectorField = generatedTable.schema.fields.find(
+      (field) => field.name === "vector",
+    );
+    expect(vectorField?.nullable).toBe(false);
+
+    await table.add(data);
+
+    const rows = await table.query().toArray();
+    expect(rows).toHaveLength(2);
+    for (const row of rows) {
+      expect([...row.vector]).toEqual([1, 2, 3]);
+    }
+  });
+
   it("should error when appending to a table with an unregistered embedding function", async () => {
     @register("mock")
     class MockEmbeddingFunction extends EmbeddingFunction<string> {

nodejs/__test__/package.test.ts

@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: Copyright The LanceDB Authors
+
+import packageJson = require("../package.json");
+
+describe("package metadata", () => {
+  it("requires Node.js type declarations compatible with the runtime", () => {
+    expect(packageJson.engines.node).toBe(">= 18");
+    expect(packageJson.peerDependencies["@types/node"]).toBe(">=18");
+    expect(packageJson.peerDependenciesMeta["@types/node"]).toEqual({
+      optional: true,
+    });
+  });
+});

nodejs/__test__/query.test.ts

@@ -110,6 +110,81 @@ describe("Query outputSchema", () => {
   });
 });
 
+describe("Search pagination", () => {
+  let tmpDir: tmp.DirResult;
+  let table: Table;
+
+  beforeEach(async () => {
+    tmpDir = tmp.dirSync({ unsafeCleanup: true });
+    const db = await connect(tmpDir.name);
+    const schema = new Schema([
+      new Field("id", new Int64(), false),
+      new Field("text", new Utf8(), false),
+      new Field(
+        "vector",
+        new FixedSizeList(2, new Field("item", new Float32())),
+        false,
+      ),
+    ]);
+    const data = makeArrowTable(
+      [
+        { id: 1n, text: "common", vector: [0, 0] },
+        { id: 2n, text: "common common", vector: [1, 1] },
+        { id: 3n, text: "common common common", vector: [2, 2] },
+        { id: 4n, text: "common common common common", vector: [3, 3] },
+      ],
+      { schema },
+    );
+    table = await db.createTable("test", data);
+  });
+
+  afterEach(() => {
+    tmpDir.removeCallback();
+  });
+
+  it("applies offset after the vector search limit", async () => {
+    const allResults = await table
+      .vectorSearch([0, 0])
+      .select(["id"])
+      .limit(4)
+      .toArray();
+    const secondPage = await table
+      .vectorSearch([0, 0])
+      .select(["id"])
+      .limit(2)
+      .offset(2)
+      .toArray();
+
+    expect(allResults).toHaveLength(4);
+    expect(secondPage).toHaveLength(2);
+    expect(secondPage.map((row) => row.id)).toEqual(
+      allResults.slice(2, 4).map((row) => row.id),
+    );
+  });
+
+  it("applies offset after the full-text search limit", async () => {
+    await table.createIndex("text", { config: Index.fts() });
+
+    const allResults = await table
+      .search("common", "fts")
+      .select(["id"])
+      .limit(4)
+      .toArray();
+    const secondPage = await table
+      .search("common", "fts")
+      .select(["id"])
+      .limit(2)
+      .offset(2)
+      .toArray();
+
+    expect(allResults).toHaveLength(4);
+    expect(secondPage).toHaveLength(2);
+    expect(secondPage.map((row) => row.id)).toEqual(
+      allResults.slice(2, 4).map((row) => row.id),
+    );
+  });
+});
+
 describe("Query orderBy", () => {
   let tmpDir: tmp.DirResult;
   let table: Table;

nodejs/__test__/remote.test.ts

@@ -1001,4 +1001,111 @@ describe("remote connection jobs surface", () => {
       },
     );
   });
+
+  it("addBases posts the bases array", async () => {
+    const postedBodies: unknown[] = [];
+    await withMockDatabase(
+      (req, res) => {
+        const path = req.url ?? "";
+        if (path.endsWith("/describe/")) {
+          res.writeHead(200, { "Content-Type": "application/json" }).end(
+            JSON.stringify({
+              name: "photos",
+              version: 1,
+              schema: { fields: [] },
+            }),
+          );
+          return;
+        }
+        if (path.endsWith("/bases/")) {
+          const chunks: Buffer[] = [];
+          req.on("data", (chunk) => chunks.push(chunk));
+          req.on("end", () => {
+            postedBodies.push(JSON.parse(Buffer.concat(chunks).toString()));
+            res
+              .writeHead(200, { "Content-Type": "application/json" })
+              .end(JSON.stringify({ version: 2 }));
+          });
+          return;
+        }
+        if (path.endsWith("/bases/list/")) {
+          res.writeHead(200, { "Content-Type": "application/json" }).end(
+            JSON.stringify({
+              bases: [
+                {
+                  path: "s3://bucket/media/",
+                  isDatasetRoot: false,
+                },
+              ],
+            }),
+          );
+          return;
+        }
+        res.writeHead(404).end();
+      },
+      async (db) => {
+        const table = await db.openTable("photos");
+        await table.addBases({ path: "s3://bucket/media/" });
+        expect(await table.listBases()).toEqual([
+          {
+            path: "s3://bucket/media/",
+            isDatasetRoot: false,
+          },
+        ]);
+      },
+    );
+    expect(postedBodies).toEqual([
+      {
+        bases: [
+          {
+            path: "s3://bucket/media/",
+            isDatasetRoot: false,
+          },
+        ],
+      },
+    ]);
+  });
+
+  it("listBases returns a named dataset-root base", async () => {
+    await withMockDatabase(
+      (req, res) => {
+        const path = req.url ?? "";
+        if (path.endsWith("/describe/")) {
+          res.writeHead(200, { "Content-Type": "application/json" }).end(
+            JSON.stringify({
+              name: "photos",
+              version: 1,
+              schema: { fields: [] },
+            }),
+          );
+          return;
+        }
+        if (path.endsWith("/bases/list/")) {
+          res.writeHead(200, { "Content-Type": "application/json" }).end(
+            JSON.stringify({
+              bases: [
+                {
+                  path: "s3://bucket/archive/",
+                  name: "archive",
+                  isDatasetRoot: true,
+                },
+              ],
+            }),
+          );
+          return;
+        }
+        res.writeHead(404).end();
+      },
+      async (db) => {
+        const table = await db.openTable("photos");
+        expect(await table.listBases()).toEqual([
+          {
+            path: "s3://bucket/archive/",
+            name: "archive",
+            isDatasetRoot: true,
+          },
+        ]);
+      },
+    );
+  });
 });

nodejs/__test__/table.test.ts

@@ -4,6 +4,7 @@
 import * as fs from "fs";
 import * as path from "path";
 import * as tmp from "tmp";
+import { pathToFileURL } from "url";
 
 import * as arrow15 from "apache-arrow-15";
 import * as arrow16 from "apache-arrow-16";
@@ -277,8 +278,16 @@ describe.each([arrow15, arrow16, arrow17, arrow18])(
         },
         numIndices: 0,
         numRows: 3,
-        totalBytes: 44,
+        // Full on-disk size of the two data files, footers and metadata included.
+        totalBytes: 684,
       });
+
+      // Index files count toward totalBytes too (only deletion files and
+      // manifests are excluded).
+      await table.createIndex("id", { config: Index.btree() });
+      const statsWithIndex = await table.stats();
+      expect(statsWithIndex.numIndices).toBe(1);
+      expect(statsWithIndex.totalBytes).toBeGreaterThan(684);
     });
 
     it("should overwrite data if asked", async () => {
@@ -3332,3 +3341,92 @@ describe("LSM merge insert", () => {
     await expect(table.query().useLsm(true).toArray()).rejects.toThrow();
   });
 });
+
+describe("computed columns", () => {
+  let tmpDir: tmp.DirResult;
+  beforeEach(() => {
+    tmpDir = tmp.dirSync({ unsafeCleanup: true });
+  });
+  afterEach(() => tmpDir.removeCallback());
+
+  it("declares a column and fills it on refresh", async () => {
+    const db = await connect(tmpDir.name);
+    const table = await db.createTable("computed", [{ x: 1 }, { x: 2 }]);
+
+    await table.addColumns({
+      computed: [{ name: "doubled", valueSql: "x * 2" }],
+    });
+    let rows = await table.query().toArray();
+    expect(rows.map((r) => r.doubled)).toEqual([null, null]);
+
+    const result = await table.refreshColumn("doubled");
+    expect(result.rowsFilled).toBe(2);
+
+    rows = await table.query().toArray();
+    expect(rows.map((r) => r.doubled).sort()).toEqual([2, 4]);
+  });
+
+  it("returns a job handle from refreshColumnAsync", async () => {
+    const db = await connect(tmpDir.name);
+    const table = await db.createTable("computed_job", [{ x: 1 }, { x: 2 }]);
+
+    await table.addColumns({
+      computed: [{ name: "doubled", valueSql: "x * 2" }],
+    });
+
+    const job = await table.refreshColumnAsync("doubled");
+    expect(job.id).toBeNull();
+    await job.wait();
+    expect(await job.status()).toBe("finished");
+
+    const rows = await table.query().toArray();
+    expect(rows.map((r) => r.doubled).sort()).toEqual([2, 4]);
+
+    // Bad input rejects at the call, not through the job.
+    await expect(table.refreshColumnAsync("x")).rejects.toThrow(
+      "not a computed column",
+    );
+  });
+
+  it("fills rows added since the last refresh", async () => {
+    const db = await connect(tmpDir.name);
+    const table = await db.createTable("computed_append", [{ x: 1 }]);
+
+    await table.addColumns({
+      computed: [{ name: "doubled", valueSql: "x * 2" }],
+    });
+    await table.refreshColumn("doubled");
+    await table.add([{ x: 5 }]);
+
+    const result = await table.refreshColumn("doubled");
+    expect(result.rowsFilled).toBe(1);
+
+    const rows = await table.query().toArray();
+    expect(rows.map((r) => r.doubled).sort()).toEqual([10, 2]);
+  });
+});
+
+describe("table bases", () => {
+  let tmpDir: tmp.DirResult;
+  beforeEach(() => {
+    tmpDir = tmp.dirSync({ unsafeCleanup: true });
+  });
+  afterEach(() => tmpDir.removeCallback());
+
+  it("listBases reflects added bases", async () => {
+    const conn = await connect(tmpDir.name);
+    const table = await conn.createEmptyTable(
+      "photos",
+      new arrow.Schema([new arrow.Field("id", new arrow.Int64(), false)]),
+    );
+    const media = path.join(tmpDir.name, "media");
+    fs.mkdirSync(media);
+    const location = pathToFileURL(media).toString();
+
+    expect(await table.listBases()).toEqual([]);
+    await table.addBases(location);
+    expect(await table.listBases()).toEqual([
+      { path: location, isDatasetRoot: false },
+    ]);
+  });
+});

nodejs/lancedb/connection.ts

@@ -327,6 +327,14 @@ export abstract class Connection {
    */
   abstract dropTable(name: string, namespacePath?: string[]): Promise<void>;
 
+  /**
+   * Start dropping a table and return its cleanup job.
+   *
+   * The table may become unavailable before its data files are removed. Wait
+   * on the returned job to know when cleanup has finished.
+   */
+  abstract dropTableAsync(name: string, namespacePath?: string[]): Promise<Job>;
+
   /**
    * Drop all tables in the database.
    * @param {string[]} namespacePath The namespace path to drop tables from (defaults to root namespace).
@@ -705,6 +713,10 @@ export class LocalConnection extends Connection {
     return this.inner.dropTable(name, namespacePath ?? []);
   }
 
+  async dropTableAsync(name: string, namespacePath?: string[]): Promise<Job> {
+    return this.inner.dropTableAsync(name, namespacePath ?? []);
+  }
+
   async dropAllTables(namespacePath?: string[]): Promise<void> {
     return this.inner.dropAllTables(namespacePath ?? []);
   }

nodejs/lancedb/index.ts

@@ -50,6 +50,7 @@ export {
   MergeResult,
   AddResult,
   AddColumnsResult,
+  RefreshColumnResult,
   AlterColumnsResult,
   UpdateFieldMetadataResult,
   DeleteResult,
@@ -129,6 +130,7 @@ export {
 
 export {
   Table,
+  TableBase,
   Branches,
   BranchColumnSummary,
   BranchColumnChange,

nodejs/lancedb/sanitize.ts

@@ -9,7 +9,7 @@
 // comes from the exact same library instance.  This is not always the case
 // and so we must sanitize the input to ensure that it is compatible.
 
-import { BufferType, Data } from "apache-arrow";
+import { BufferType, Data, Vector } from "apache-arrow";
 import type { IntBitWidth, TKeys, TimeBitWidth } from "apache-arrow/type";
 import {
   Binary,
@@ -74,6 +74,20 @@ import {
   Utf8,
 } from "./arrow";
 
+type SanitizationContext = {
+  types: WeakMap<object, DataType>;
+  vectors: WeakMap<object, Vector>;
+  data: WeakMap<object, Data<DataType>>;
+};
+
+function createSanitizationContext(): SanitizationContext {
+  return {
+    types: new WeakMap(),
+    vectors: new WeakMap(),
+    data: new WeakMap(),
+  };
+}
+
 export function sanitizeMetadata(
   metadataLike?: unknown,
 ): Map<string, string> | undefined {
@@ -186,6 +200,13 @@ export function sanitizeInterval(typeLike: object) {
 }
 
 export function sanitizeList(typeLike: object) {
+  return sanitizeListWithContext(typeLike, createSanitizationContext());
+}
+
+function sanitizeListWithContext(
+  typeLike: object,
+  context: SanitizationContext,
+) {
   if (!("children" in typeLike) || !Array.isArray(typeLike.children)) {
     throw Error(
       "Expected a List type to have an array-like `children` property",
@@ -194,19 +215,35 @@ export function sanitizeList(typeLike: object) {
   if (typeLike.children.length !== 1) {
     throw Error("Expected a List type to have exactly one child");
   }
-  return new List(sanitizeField(typeLike.children[0]));
+  return new List(sanitizeFieldWithContext(typeLike.children[0], context));
 }
 
 export function sanitizeStruct(typeLike: object) {
+  return sanitizeStructWithContext(typeLike, createSanitizationContext());
+}
+
+function sanitizeStructWithContext(
+  typeLike: object,
+  context: SanitizationContext,
+) {
   if (!("children" in typeLike) || !Array.isArray(typeLike.children)) {
     throw Error(
       "Expected a Struct type to have an array-like `children` property",
     );
   }
-  return new Struct(typeLike.children.map((child) => sanitizeField(child)));
+  return new Struct(
+    typeLike.children.map((child) => sanitizeFieldWithContext(child, context)),
+  );
 }
 
 export function sanitizeUnion(typeLike: object) {
+  return sanitizeUnionWithContext(typeLike, createSanitizationContext());
+}
+
+function sanitizeUnionWithContext(
+  typeLike: object,
+  context: SanitizationContext,
+) {
   if (
     !("typeIds" in typeLike) ||
     !("mode" in typeLike) ||
@@ -226,7 +263,7 @@ export function sanitizeUnion(typeLike: object) {
     typeLike.mode,
     // biome-ignore lint/suspicious/noExplicitAny: skip
     typeLike.typeIds as any,
-    typeLike.children.map((child) => sanitizeField(child)),
+    typeLike.children.map((child) => sanitizeFieldWithContext(child, context)),
   );
 }
 
@@ -234,6 +271,19 @@ export function sanitizeTypedUnion(
   typeLike: object,
   // eslint-disable-next-line @typescript-eslint/naming-convention
   UnionType: typeof DenseUnion | typeof SparseUnion,
+) {
+  return sanitizeTypedUnionWithContext(
+    typeLike,
+    UnionType,
+    createSanitizationContext(),
+  );
+}
+
+function sanitizeTypedUnionWithContext(
+  typeLike: object,
+  // eslint-disable-next-line @typescript-eslint/naming-convention
+  UnionType: typeof DenseUnion | typeof SparseUnion,
+  context: SanitizationContext,
 ) {
   if (!("typeIds" in typeLike)) {
     throw Error(
@@ -248,7 +298,7 @@ export function sanitizeTypedUnion(
 
   return new UnionType(
     typeLike.typeIds as Int32Array | number[],
-    typeLike.children.map((child) => sanitizeField(child)),
+    typeLike.children.map((child) => sanitizeFieldWithContext(child, context)),
   );
 }
 
@@ -262,6 +312,16 @@ export function sanitizeFixedSizeBinary(typeLike: object) {
 }
 
 export function sanitizeFixedSizeList(typeLike: object) {
+  return sanitizeFixedSizeListWithContext(
+    typeLike,
+    createSanitizationContext(),
+  );
+}
+
+function sanitizeFixedSizeListWithContext(
+  typeLike: object,
+  context: SanitizationContext,
+) {
   if (!("listSize" in typeLike) || typeof typeLike.listSize !== "number") {
     throw Error("Expected a FixedSizeList type to have a `listSize` property");
   }
@@ -275,11 +335,18 @@ export function sanitizeFixedSizeList(typeLike: object) {
   }
   return new FixedSizeList(
     typeLike.listSize,
-    sanitizeField(typeLike.children[0]),
+    sanitizeFieldWithContext(typeLike.children[0], context),
   );
 }
 
 export function sanitizeMap(typeLike: object) {
+  return sanitizeMapWithContext(typeLike, createSanitizationContext());
+}
+
+function sanitizeMapWithContext(
+  typeLike: object,
+  context: SanitizationContext,
+) {
   if (!("children" in typeLike) || !Array.isArray(typeLike.children)) {
     throw Error(
       "Expected a Map type to have an array-like `children` property",
@@ -292,7 +359,10 @@ export function sanitizeMap(typeLike: object) {
     throw Error("Expected a Map type to have exactly one child");
   }
 
-  return new Map_(sanitizeField(typeLike.children[0]), typeLike.keysSorted);
+  return new Map_(
+    sanitizeFieldWithContext(typeLike.children[0], context),
+    typeLike.keysSorted,
+  );
 }
 
 export function sanitizeDuration(typeLike: object) {
@@ -303,6 +373,13 @@ export function sanitizeDuration(typeLike: object) {
 }
 
 export function sanitizeDictionary(typeLike: object) {
+  return sanitizeDictionaryWithContext(typeLike, createSanitizationContext());
+}
+
+function sanitizeDictionaryWithContext(
+  typeLike: object,
+  context: SanitizationContext,
+) {
   if (!("id" in typeLike) || typeof typeLike.id !== "number") {
     throw Error("Expected a Dictionary type to have an `id` property");
   }
@@ -316,8 +393,8 @@ export function sanitizeDictionary(typeLike: object) {
     throw Error("Expected a Dictionary type to have an `isOrdered` property");
   }
   return new Dictionary(
-    sanitizeType(typeLike.dictionary),
-    sanitizeType(typeLike.indices) as TKeys,
+    sanitizeTypeWithContext(typeLike.dictionary, context),
+    sanitizeTypeWithContext(typeLike.indices, context) as TKeys,
     typeLike.id,
     typeLike.isOrdered,
   );
@@ -325,12 +402,23 @@ export function sanitizeDictionary(typeLike: object) {
 
 // biome-ignore lint/suspicious/noExplicitAny: skip
 export function sanitizeType(typeLike: unknown): DataType<any> {
+  return sanitizeTypeWithContext(typeLike, createSanitizationContext());
+}
+
+function sanitizeTypeWithContext(
+  typeLike: unknown,
+  context: SanitizationContext,
+): DataType {
   if (typeof typeLike === "string") {
     return dataTypeFromName(typeLike);
   }
   if (typeof typeLike !== "object" || typeLike === null) {
     throw Error("Expected a Type but object was null/undefined");
   }
+  const cached = context.types.get(typeLike);
+  if (cached !== undefined) {
+    return cached;
+  }
   if (
     !("typeId" in typeLike) ||
     !(
@@ -349,6 +437,16 @@ export function sanitizeType(typeLike: unknown): DataType<any> {
     throw Error("Type's typeId property was not a function or number");
   }
 
+  const type = sanitizeTypeById(typeLike, typeId, context);
+  context.types.set(typeLike, type);
+  return type;
+}
+
+function sanitizeTypeById(
+  typeLike: object,
+  typeId: Type,
+  context: SanitizationContext,
+): DataType {
   switch (typeId) {
     case Type.NONE:
       throw Error("Received a Type with a typeId of NONE");
@@ -375,21 +473,21 @@ export function sanitizeType(typeLike: unknown): DataType<any> {
     case Type.Interval:
       return sanitizeInterval(typeLike);
     case Type.List:
-      return sanitizeList(typeLike);
+      return sanitizeListWithContext(typeLike, context);
     case Type.Struct:
-      return sanitizeStruct(typeLike);
+      return sanitizeStructWithContext(typeLike, context);
     case Type.Union:
-      return sanitizeUnion(typeLike);
+      return sanitizeUnionWithContext(typeLike, context);
     case Type.FixedSizeBinary:
       return sanitizeFixedSizeBinary(typeLike);
     case Type.FixedSizeList:
-      return sanitizeFixedSizeList(typeLike);
+      return sanitizeFixedSizeListWithContext(typeLike, context);
     case Type.Map:
-      return sanitizeMap(typeLike);
+      return sanitizeMapWithContext(typeLike, context);
     case Type.Duration:
       return sanitizeDuration(typeLike);
     case Type.Dictionary:
-      return sanitizeDictionary(typeLike);
+      return sanitizeDictionaryWithContext(typeLike, context);
     case Type.Int8:
       return new Int8();
     case Type.Int16:
@@ -433,9 +531,9 @@ export function sanitizeType(typeLike: unknown): DataType<any> {
     case Type.TimestampSecond:
       return sanitizeTypedTimestamp(typeLike, TimestampSecond);
     case Type.DenseUnion:
-      return sanitizeTypedUnion(typeLike, DenseUnion);
+      return sanitizeTypedUnionWithContext(typeLike, DenseUnion, context);
     case Type.SparseUnion:
-      return sanitizeTypedUnion(typeLike, SparseUnion);
+      return sanitizeTypedUnionWithContext(typeLike, SparseUnion, context);
     case Type.IntervalDayTime:
       return new IntervalDayTime();
     case Type.IntervalYearMonth:
@@ -454,6 +552,13 @@ export function sanitizeType(typeLike: unknown): DataType<any> {
 }
 
 export function sanitizeField(fieldLike: unknown): Field {
+  return sanitizeFieldWithContext(fieldLike, createSanitizationContext());
+}
+
+function sanitizeFieldWithContext(
+  fieldLike: unknown,
+  context: SanitizationContext,
+): Field {
   if (fieldLike instanceof Field) {
     return fieldLike;
   }
@@ -471,7 +576,7 @@ export function sanitizeField(fieldLike: unknown): Field {
   }
   let type: DataType;
   try {
-    type = sanitizeType(fieldLike.type);
+    type = sanitizeTypeWithContext(fieldLike.type, context);
   } catch (error: unknown) {
     throw Error(
       `Unable to sanitize type for field: ${fieldLike.name} due to error: ${error}`,
@@ -501,6 +606,13 @@ export function sanitizeField(fieldLike: unknown): Field {
  * than lancedb is using.
  */
 export function sanitizeSchema(schemaLike: SchemaLike): Schema {
+  return sanitizeSchemaWithContext(schemaLike, createSanitizationContext());
+}
+
+function sanitizeSchemaWithContext(
+  schemaLike: SchemaLike,
+  context: SanitizationContext,
+): Schema {
   if (schemaLike instanceof Schema) {
     return schemaLike;
   }
@@ -522,7 +634,7 @@ export function sanitizeSchema(schemaLike: SchemaLike): Schema {
     );
   }
   const sanitizedFields = schemaLike.fields.map((field) =>
-    sanitizeField(field),
+    sanitizeFieldWithContext(field, context),
   );
   return new Schema(sanitizedFields, metadata);
 }
@@ -544,13 +656,18 @@ export function sanitizeTable(tableLike: TableLike): Table {
       "The table passed in does not appear to be a table (no 'columns' property)",
     );
   }
-  const schema = sanitizeSchema(tableLike.schema);
-
-  const batches = tableLike.batches.map(sanitizeRecordBatch);
+  const context = createSanitizationContext();
+  const schema = sanitizeSchemaWithContext(tableLike.schema, context);
+  const batches = tableLike.batches.map((batch) =>
+    sanitizeRecordBatch(batch, context),
+  );
   return new Table(schema, batches);
 }
 
-function sanitizeRecordBatch(batchLike: RecordBatchLike): RecordBatch {
+function sanitizeRecordBatch(
+  batchLike: RecordBatchLike,
+  context: SanitizationContext,
+): RecordBatch {
   if (batchLike instanceof RecordBatch) {
     return batchLike;
   }
@@ -567,19 +684,43 @@ function sanitizeRecordBatch(batchLike: RecordBatchLike): RecordBatch {
       "The record batch passed in does not appear to be a record batch (no 'data' property)",
     );
   }
-  const schema = sanitizeSchema(batchLike.schema);
-  const data = sanitizeData(batchLike.data);
+  const schema = sanitizeSchemaWithContext(batchLike.schema, context);
+  const data = sanitizeData(batchLike.data, context) as Data<Struct>;
   return new RecordBatch(schema, data);
 }
+
+type DictionaryVectorLike = {
+  data: readonly DataLike[];
+};
+
+type DictionaryDataLike = DataLike & {
+  dictionary?: DictionaryVectorLike;
+};
+
 function sanitizeData(
   dataLike: DataLike,
-  // biome-ignore lint/suspicious/noExplicitAny: <explanation>
-): import("apache-arrow").Data<Struct<any>> {
+  context: SanitizationContext,
+): Data<DataType> {
   if (dataLike instanceof Data) {
     return dataLike;
   }
-  return new Data(
-    dataLike.type,
+  const cachedData = context.data.get(dataLike);
+  if (cachedData !== undefined) {
+    return cachedData;
+  }
+  const dictionaryLike = (dataLike as DictionaryDataLike).dictionary;
+  let dictionary: Vector | undefined;
+  if (dictionaryLike !== undefined) {
+    dictionary = context.vectors.get(dictionaryLike);
+    if (dictionary === undefined) {
+      dictionary = new Vector(
+        dictionaryLike.data.map((data) => sanitizeData(data, context)),
+      );
+      context.vectors.set(dictionaryLike, dictionary);
+    }
+  }
+  const data = new Data(
+    sanitizeTypeWithContext(dataLike.type, context),
     dataLike.offset,
     dataLike.length,
     dataLike.nullCount,
@@ -589,7 +730,11 @@ function sanitizeData(
       [BufferType.VALIDITY]: dataLike.nullBitmap,
       [BufferType.TYPE]: dataLike.typeIds,
     },
+    dataLike.children.map((child) => sanitizeData(child, context)),
+    dictionary,
   );
+  context.data.set(dataLike, data);
+  return data;
 }
 
 const constructorsByTypeName = {

nodejs/lancedb/table.ts

@@ -33,6 +33,7 @@ import {
   Job,
   Branches as NativeBranches,
   OptimizeStats,
+  RefreshColumnResult,
   TableStatistics,
   Tags,
   UpdateFieldMetadataResult,
@@ -77,6 +78,25 @@ export interface WriteProgress {
   done: boolean;
 }
 
+/**
+ * An extra storage prefix registered on a table.
+ *
+ * `path` is an object-store URI. `name` is an optional alias. `isDatasetRoot`
+ * is true when `path` points to a Lance dataset root. When false, `path`
+ * points directly to the directory containing the referenced files.
+ */
+export interface TableBase {
+  /** Object store URI such as `s3://bucket/media/`. */
+  path: string;
+  /** Optional alias. */
+  name?: string;
+  /**
+   * True when `path` is a Lance dataset root. When false, `path` is the
+   * directory containing the referenced files.
+   */
+  isDatasetRoot?: boolean;
+}
+
 /**
  * Options for adding data to a table.
  */
@@ -197,7 +217,11 @@ export interface LsmWriteSpec {
   column?: string;
   /** Bucket variant: the number of buckets, in `[1, 1024]`. */
   numBuckets?: number;
-  /** Names of indexes the MemWAL should keep up to date during writes. */
+  /**
+   * Indexes the MemWAL keeps up to date. Omit to maintain every supported
+   * index, resolved on install — a snapshot, so indexes created later are not
+   * maintained. Pass `[]` for none.
+   */
   maintainedIndexes?: string[];
   /** Default `ShardWriter` configuration recorded in the MemWAL index. */
   writerConfigDefaults?: Record<string, string>;
@@ -521,18 +545,87 @@ export abstract class Table {
   abstract vectorSearch(vector: IntoVector | MultiVector): VectorQuery;
   /**
    * Add new columns with defined values.
+   *
+   * The `{ computed }` form stores the expression rather than evaluating it
+   * now: the column is committed with no values, and rows get them from
+   * {@link Table#refreshColumn}. Declaring one therefore costs the same on a
+   * large table as on an empty one.
+   *
+   * A refresh does not revisit rows it has already filled, so mutating an
+   * input leaves the value computed at fill time; recomputing means dropping
+   * the column and declaring it again. While a declaration reads a column,
+   * that column cannot be renamed, retyped or dropped.
+   *
+   * On LanceDB Cloud and Enterprise the expression is planned by the
+   * server, and the refresh runs as a server job -- see
+   * {@link Table#refreshColumnAsync}.
    * @param {AddColumnsSql[] | Field | Field[] | Schema} newColumnTransforms Either:
    *   - An array of objects with column names and SQL expressions to calculate values
    *   - A single Arrow Field defining one column with its data type (column will be initialized with null values)
    *   - An array of Arrow Fields defining columns with their data types (columns will be initialized with null values)
    *   - An Arrow Schema defining columns with their data types (columns will be initialized with null values)
+   *   - `{ computed }`, declaring columns defined by a SQL expression whose type and inputs are derived from it
    * @returns {Promise<AddColumnsResult>} A promise that resolves to an object
    * containing the new version number of the table after adding the columns.
+   * @example
+   * ```ts
+   * await table.addColumns({ computed: [{ name: "doubled", valueSql: "x * 2" }] });
+   * const { rowsFilled } = await table.refreshColumn("doubled");
+   * ```
    */
   abstract addColumns(
-    newColumnTransforms: AddColumnsSql[] | Field | Field[] | Schema,
+    newColumnTransforms:
+      | AddColumnsSql[]
+      | Field
+      | Field[]
+      | Schema
+      | { computed: AddColumnsSql[] },
   ): Promise<AddColumnsResult>;
 
+  /**
+   * Register additional storage bases for this table.
+   *
+   * A URI string is a non-root base with no alias.
+   */
+  abstract addBases(
+    bases: string | TableBase | Array<string | TableBase>,
+  ): Promise<void>;
+
+  /** Return the additional storage bases for the current table snapshot. */
+  abstract listBases(): Promise<TableBase[]>;
+
+  /**
+   * Fill the rows of a computed column that hold no value yet.
+   *
+   * Rows appended since the last refresh are filled by the next one; rows
+   * already filled are left as they are, so the call is idempotent and does
+   * not observe a mutated input. Local tables only: a remote refresh runs
+   * as a server job, through {@link Table#refreshColumnAsync}.
+   * @param {string} column The name of the computed column to fill.
+   * @returns {Promise<RefreshColumnResult>} A promise that resolves to the
+   * number of rows filled and the new version number of the table.
+   */
+  abstract refreshColumn(column: string): Promise<RefreshColumnResult>;
+
+  /**
+   * Like {@link Table#refreshColumn}, but returns a handle to the refresh
+   * job instead of blocking until it completes.
+   *
+   * The job may already be complete when returned; callers must not assume
+   * the column is filled until {@link Job.wait} resolves. Invalid input --
+   * an unknown column, or one that is not computed -- rejects here rather
+   * than failing the job. On local tables the job runs in-process; on
+   * LanceDB Cloud and Enterprise it is the server's backfill job.
+   * @param {string} column The name of the computed column to fill.
+   * @example
+   * ```ts
+   * const job = await table.refreshColumnAsync("doubled");
+   * await job.wait();
+   * console.log(await job.status()); // "finished"
+   * ```
+   */
+  abstract refreshColumnAsync(column: string): Promise<Job>;
+
   /**
    * Alter the name or nullability of columns.
    * @param {ColumnAlteration[]} columnAlterations One or more alterations to
@@ -595,6 +688,11 @@ export abstract class Table {
    * All variants require the table to have an unenforced primary key
    * ({@link Table#setUnenforcedPrimaryKey}); bucket sharding additionally
    * requires it to be the single column being bucketed.
+   *
+   * Omitting `maintainedIndexes` maintains every index on the table, resolved
+   * here, failing if one cannot be maintained — name them to install anyway.
+   * Naming them pins an exact set, and a still-building index is rejected
+   * rather than quietly omitted.
    * @param {LsmWriteSpec} spec The sharding spec to install.
    * @returns {Promise<void>}
    * @example
@@ -622,9 +720,10 @@ export abstract class Table {
    *
    * Resolves to `undefined` when the MemWAL LSM write path is not enabled (no
    * spec has been set, or it was removed with {@link Table#unsetLsmWriteSpec}).
-   * The returned spec — including its `maintainedIndexes` and
-   * `writerConfigDefaults` — mirrors what was passed to
-   * {@link Table#setLsmWriteSpec}.
+   * The returned spec mirrors what was passed to
+   * {@link Table#setLsmWriteSpec}, except that `maintainedIndexes` always
+   * reports the concrete list resolved when the spec was set — `undefined`
+   * never round-trips.
    * @returns {Promise<LsmWriteSpec | undefined>}
    */
   abstract getLsmWriteSpec(): Promise<LsmWriteSpec | undefined>;
@@ -1078,8 +1177,22 @@ export class LocalTable extends Table {
   // TODO: Support BatchUDF
 
   async addColumns(
-    newColumnTransforms: AddColumnsSql[] | Field | Field[] | Schema,
+    newColumnTransforms:
+      | AddColumnsSql[]
+      | Field
+      | Field[]
+      | Schema
+      | { computed: AddColumnsSql[] },
   ): Promise<AddColumnsResult> {
+    // Columns defined by an expression are declared, not materialized here.
+    if (
+      typeof newColumnTransforms === "object" &&
+      !Array.isArray(newColumnTransforms) &&
+      "computed" in newColumnTransforms
+    ) {
+      return await this.inner.addComputedColumns(newColumnTransforms.computed);
+    }
+
     // Handle single Field -> convert to array of Fields
     if (newColumnTransforms instanceof Field) {
       newColumnTransforms = [newColumnTransforms];
@@ -1114,6 +1227,24 @@ export class LocalTable extends Table {
     throw new Error("Invalid input type for addColumns");
   }
 
+  async addBases(
+    bases: string | TableBase | Array<string | TableBase>,
+  ): Promise<void> {
+    await this.inner.addBases(normalizeBases(bases));
+  }
+
+  async listBases(): Promise<TableBase[]> {
+    return await this.inner.listBases();
+  }
+
+  async refreshColumn(column: string): Promise<RefreshColumnResult> {
+    return await this.inner.refreshColumn(column);
+  }
+
+  async refreshColumnAsync(column: string): Promise<Job> {
+    return await this.inner.refreshColumnAsync(column);
+  }
+
   async alterColumns(
     columnAlterations: ColumnAlteration[],
   ): Promise<AlterColumnsResult> {
@@ -1306,6 +1437,21 @@ export class LocalTable extends Table {
   }
 }
 
+function normalizeBases(
+  bases: string | TableBase | Array<string | TableBase>,
+): TableBase[] {
+  const baseInputs = Array.isArray(bases) ? bases : [bases];
+  return baseInputs.map((base) =>
+    typeof base === "string"
+      ? { path: base, isDatasetRoot: false }
+      : {
+          path: base.path,
+          name: base.name,
+          isDatasetRoot: base.isDatasetRoot ?? false,
+        },
+  );
+}
+
 /**
  *  A definition of a column alteration. The alteration changes the column at
  * `path` to have the new name `name`, to be nullable if `nullable` is true,

nodejs/npm/darwin-arm64/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@lancedb/lancedb-darwin-arm64",
-	"version": "0.37.1-beta.0",
+	"version": "0.38.0-beta.0",
 	"os": ["darwin"],
 	"cpu": ["arm64"],
 	"main": "lancedb.darwin-arm64.node",

nodejs/npm/linux-arm64-gnu/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@lancedb/lancedb-linux-arm64-gnu",
-	"version": "0.37.1-beta.0",
+	"version": "0.38.0-beta.0",
 	"os": ["linux"],
 	"cpu": ["arm64"],
 	"main": "lancedb.linux-arm64-gnu.node",

nodejs/npm/linux-arm64-musl/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@lancedb/lancedb-linux-arm64-musl",
-	"version": "0.37.1-beta.0",
+	"version": "0.38.0-beta.0",
 	"os": ["linux"],
 	"cpu": ["arm64"],
 	"main": "lancedb.linux-arm64-musl.node",

nodejs/npm/linux-x64-gnu/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@lancedb/lancedb-linux-x64-gnu",
-	"version": "0.37.1-beta.0",
+	"version": "0.38.0-beta.0",
 	"os": ["linux"],
 	"cpu": ["x64"],
 	"main": "lancedb.linux-x64-gnu.node",

nodejs/npm/linux-x64-musl/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@lancedb/lancedb-linux-x64-musl",
-	"version": "0.37.1-beta.0",
+	"version": "0.38.0-beta.0",
 	"os": ["linux"],
 	"cpu": ["x64"],
 	"main": "lancedb.linux-x64-musl.node",

nodejs/npm/win32-arm64-msvc/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@lancedb/lancedb-win32-arm64-msvc",
-  "version": "0.37.1-beta.0",
+  "version": "0.38.0-beta.0",
   "os": [
     "win32"
   ],

nodejs/npm/win32-x64-msvc/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@lancedb/lancedb-win32-x64-msvc",
-	"version": "0.37.1-beta.0",
+	"version": "0.38.0-beta.0",
 	"os": ["win32"],
 	"cpu": ["x64"],
 	"main": "lancedb.win32-x64-msvc.node",

nodejs/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "@lancedb/lancedb",
-  "version": "0.37.1-beta.0",
+  "version": "0.38.0-beta.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@lancedb/lancedb",
-      "version": "0.37.1-beta.0",
+      "version": "0.38.0-beta.0",
       "cpu": [
         "x64",
         "arm64"
@@ -55,7 +55,13 @@
         "openai": "4.29.2"
       },
       "peerDependencies": {
+        "@types/node": ">=18",
         "apache-arrow": ">=15.0.0 <=18.1.0"
+      },
+      "peerDependenciesMeta": {
+        "@types/node": {
+          "optional": true
+        }
       }
     },
     "node_modules/@aws-crypto/crc32": {

nodejs/package.json

@@ -11,7 +11,7 @@
     "ann"
   ],
   "private": false,
-  "version": "0.37.1-beta.0",
+  "version": "0.38.0-beta.0",
   "main": "dist/index.js",
   "exports": {
     ".": "./dist/index.js",
@@ -101,6 +101,12 @@
     "openai": "4.29.2"
   },
   "peerDependencies": {
+    "@types/node": ">=18",
     "apache-arrow": ">=15.0.0 <=18.1.0"
+  },
+  "peerDependenciesMeta": {
+    "@types/node": {
+      "optional": true
+    }
   }
 }

nodejs/src/connection.rs

@@ -334,6 +334,22 @@ impl Connection {
             .default_error()
     }
 
+    /// Start dropping a table and return its cleanup job.
+    #[napi(catch_unwind)]
+    pub async fn drop_table_async(
+        &self,
+        name: String,
+        namespace_path: Option<Vec<String>>,
+    ) -> napi::Result<crate::job::Job> {
+        let ns = namespace_path.unwrap_or_default();
+        let job = self
+            .get_inner()?
+            .drop_table_async(&name, &ns)
+            .await
+            .default_error()?;
+        Ok(crate::job::Job::new(job))
+    }
+
     #[napi(catch_unwind)]
     pub async fn drop_all_tables(&self, namespace_path: Option<Vec<String>>) -> napi::Result<()> {
         let ns = namespace_path.unwrap_or_default();

nodejs/src/table.rs

@@ -10,6 +10,7 @@ use lancedb::table::{
     AddDataMode, ColumnAlteration as LanceColumnAlteration, Duration,
     FieldMetadataUpdate as LanceFieldMetadataUpdate, FtsToken as LanceDbFtsToken,
     NewColumnTransform, OptimizeAction, OptimizeOptions, Ref, Table as LanceDbTable,
+    TableBase as LanceTableBase,
 };
 use napi::bindgen_prelude::*;
 use napi::threadsafe_function::{ThreadsafeFunction, ThreadsafeFunctionCallMode};
@@ -347,6 +348,40 @@ impl Table {
         Ok(res.into())
     }
 
+    #[napi(catch_unwind)]
+    pub async fn add_computed_columns(
+        &self,
+        columns: Vec<AddColumnsSql>,
+    ) -> napi::Result<AddColumnsResult> {
+        let table = self.inner_ref()?;
+        let mut builder = table.add_columns();
+        for column in columns {
+            builder = builder.computed(column.name, column.value_sql);
+        }
+        let res = builder.execute().await.default_error()?;
+        Ok(res.into())
+    }
+
+    #[napi(catch_unwind)]
+    pub async fn refresh_column(&self, column: String) -> napi::Result<RefreshColumnResult> {
+        let res = self
+            .inner_ref()?
+            .refresh_column(column)
+            .await
+            .default_error()?;
+        Ok(res.into())
+    }
+
+    #[napi(catch_unwind)]
+    pub async fn refresh_column_async(&self, column: String) -> napi::Result<crate::job::Job> {
+        let job = self
+            .inner_ref()?
+            .refresh_column_async(column)
+            .await
+            .default_error()?;
+        Ok(crate::job::Job::new(job))
+    }
+
     #[napi(catch_unwind)]
     pub async fn add_columns_with_schema(
         &self,
@@ -412,6 +447,30 @@ impl Table {
         Ok(res.into())
     }
 
+    #[napi(catch_unwind)]
+    pub async fn add_bases(&self, bases: Vec<TableBase>) -> napi::Result<()> {
+        self.inner_ref()?
+            .add_bases(bases.into_iter().map(|base| LanceTableBase {
+                path: base.path,
+                name: base.name,
+                is_dataset_root: base.is_dataset_root,
+            }))
+            .await
+            .default_error()
+    }
+
+    #[napi(catch_unwind)]
+    pub async fn list_bases(&self) -> napi::Result<Vec<TableBase>> {
+        Ok(self
+            .inner_ref()?
+            .list_bases()
+            .await
+            .default_error()?
+            .into_iter()
+            .map(TableBase::from)
+            .collect())
+    }
+
     #[napi(catch_unwind)]
     pub async fn drop_columns(&self, columns: Vec<String>) -> napi::Result<DropColumnsResult> {
         let col_refs = columns.iter().map(String::as_str).collect::<Vec<_>>();
@@ -666,6 +725,28 @@ impl Table {
     }
 }
 
+#[napi(object)]
+/// An extra storage prefix registered on a table.
+pub struct TableBase {
+    /// Object store URI such as `s3://bucket/media/`.
+    pub path: String,
+    /// Optional alias.
+    pub name: Option<String>,
+    /// True when `path` is a Lance dataset root. When false, `path` is the
+    /// directory containing the referenced files.
+    pub is_dataset_root: bool,
+}
+
+impl From<LanceTableBase> for TableBase {
+    fn from(base: LanceTableBase) -> Self {
+        Self {
+            path: base.path,
+            name: base.name,
+            is_dataset_root: base.is_dataset_root,
+        }
+    }
+}
+
 #[napi(object)]
 /// A description of an index currently configured on a column
 pub struct IndexConfig {
@@ -772,7 +853,8 @@ pub struct LsmWriteSpec {
     pub column: Option<String>,
     /// Bucket variant: the number of buckets, in `[1, 1024]`.
     pub num_buckets: Option<u32>,
-    /// Names of indexes the MemWAL should keep up to date during writes.
+    /// Indexes the MemWAL keeps up to date. Omitted resolves every
+    /// maintainable index on install; an empty array means none.
     pub maintained_indexes: Option<Vec<String>>,
     /// Default `ShardWriter` configuration recorded in the MemWAL index.
     pub writer_config_defaults: Option<HashMap<String, String>>,
@@ -782,7 +864,6 @@ impl TryFrom<LsmWriteSpec> for lancedb::table::LsmWriteSpec {
     type Error = napi::Error;
 
     fn try_from(value: LsmWriteSpec) -> napi::Result<Self> {
-        let maintained = value.maintained_indexes.unwrap_or_default();
         let writer_config_defaults = value.writer_config_defaults.unwrap_or_default();
         let spec = match value.spec_type.as_str() {
             "bucket" => {
@@ -809,7 +890,7 @@ impl TryFrom<LsmWriteSpec> for lancedb::table::LsmWriteSpec {
             }
         };
         Ok(spec
-            .with_maintained_indexes(maintained)
+            .with_maintained_indexes(value.maintained_indexes)
             .with_writer_config_defaults(writer_config_defaults))
     }
 }
@@ -827,7 +908,7 @@ impl From<lancedb::table::LsmWriteSpec> for LsmWriteSpec {
                 spec_type: "bucket".to_string(),
                 column: Some(column),
                 num_buckets: Some(num_buckets),
-                maintained_indexes: Some(maintained_indexes),
+                maintained_indexes,
                 writer_config_defaults: Some(writer_config_defaults),
             },
             Native::Identity {
@@ -838,7 +919,7 @@ impl From<lancedb::table::LsmWriteSpec> for LsmWriteSpec {
                 spec_type: "identity".to_string(),
                 column: Some(column),
                 num_buckets: None,
-                maintained_indexes: Some(maintained_indexes),
+                maintained_indexes,
                 writer_config_defaults: Some(writer_config_defaults),
             },
             Native::Unsharded {
@@ -848,7 +929,7 @@ impl From<lancedb::table::LsmWriteSpec> for LsmWriteSpec {
                 spec_type: "unsharded".to_string(),
                 column: None,
                 num_buckets: None,
-                maintained_indexes: Some(maintained_indexes),
+                maintained_indexes,
                 writer_config_defaults: Some(writer_config_defaults),
             },
         }
@@ -1043,7 +1124,10 @@ impl From<lancedb::index::IndexStatistics> for IndexStatistics {
 
 #[napi(object)]
 pub struct TableStatistics {
-    /// The total number of bytes in the table
+    /// The total size, in bytes, of the table's data files, index files, and
+    /// overlay files
+    ///
+    /// Read from the manifest, so this excludes deletion files and manifests.
     pub total_bytes: i64,
 
     /// The number of rows in the table
@@ -1193,6 +1277,21 @@ pub struct AddColumnsResult {
     pub version: i64,
 }
 
+#[napi(object)]
+pub struct RefreshColumnResult {
+    pub rows_filled: i64,
+    pub version: i64,
+}
+
+impl From<lancedb::table::RefreshColumnResult> for RefreshColumnResult {
+    fn from(value: lancedb::table::RefreshColumnResult) -> Self {
+        Self {
+            rows_filled: value.rows_filled as i64,
+            version: value.version as i64,
+        }
+    }
+}
+
 impl From<lancedb::table::AddColumnsResult> for AddColumnsResult {
     fn from(value: lancedb::table::AddColumnsResult) -> Self {
         Self {

python/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "lancedb-python"
-version = "0.37.1-beta.0"
+version = "0.38.0-beta.0"
 publish = false
 edition.workspace = true
 description = "Python bindings for LanceDB"

python/pyproject.toml

@@ -60,7 +60,7 @@ tests = [
     "pytest-asyncio>=0.21",
     "duckdb>=0.9.0",
     "pytz>=2023.3",
-    "polars>=0.19, <=1.3.0",
+    "polars>=0.19, <=1.32.3",
     "pyarrow<25",
     "pyarrow-stubs>=16.0",
     "pylance==9.0.0rc1",
@@ -140,6 +140,7 @@ include = [
     "python/lancedb/remote/errors.py",
     "python/lancedb/embeddings/__init__.py",
     "python/lancedb/_lancedb.pyi",
+    "python/type_tests/connect.py",
 ]
 exclude = ["python/tests/"]
 pythonVersion = "3.13"

python/python/lancedb/__init__.py

@@ -21,7 +21,7 @@ from .remote.db import RemoteDBConnection
 from .expr import Expr, col, lit, func
 from .schema import blob, vector, BlobType
 from .job import AsyncJob, Job
-from .table import AsyncTable, Table
+from .table import AsyncTable, Table, TableBase
 from .types import BaseTokenizerType
 from ._lancedb import Session
 from .namespace import (
@@ -521,5 +521,6 @@ __all__ = [
     "RemoteDBConnection",
     "Session",
     "Table",
+    "TableBase",
     "__version__",
 ]

python/python/lancedb/_lancedb.pyi

@@ -198,6 +198,9 @@ class Connection(object):
     async def drop_table(
         self, name: str, namespace_path: Optional[List[str]] = None
     ) -> None: ...
+    async def drop_table_async(
+        self, name: str, namespace_path: Optional[List[str]] = None
+    ) -> Job: ...
     async def drop_all_tables(
         self, namespace_path: Optional[List[str]] = None
     ) -> None: ...
@@ -335,6 +338,11 @@ class Table:
     ) -> list[FtsToken]: ...
     async def delete(self, filter: Union[str, PyExpr]) -> DeleteResult: ...
     async def add_columns(self, columns: list[tuple[str, str]]) -> AddColumnsResult: ...
+    async def add_computed_columns(
+        self, columns: list[tuple[str, str]]
+    ) -> AddColumnsResult: ...
+    async def refresh_column(self, column: str) -> RefreshColumnResult: ...
+    async def refresh_column_async(self, column: str) -> Job: ...
     async def add_columns_with_schema(self, schema: pa.Schema) -> AddColumnsResult: ...
     async def alter_columns(
         self, columns: list[dict[str, Any]]
@@ -355,6 +363,10 @@ class Table:
     async def set_lsm_write_spec(self, spec: LsmWriteSpec) -> None: ...
     async def unset_lsm_write_spec(self) -> None: ...
     async def get_lsm_write_spec(self) -> Optional[LsmWriteSpec]: ...
+    async def checkpoint_lsm(self) -> None: ...
+    async def flush_lsm(self) -> None: ...
+    async def compact_lsm(self) -> None: ...
+    async def get_lsm_stats(self, include_generation_rows: bool) -> Optional[dict]: ...
     async def close_lsm_writers(self) -> None: ...
     @property
     def tags(self) -> Tags: ...
@@ -365,6 +377,8 @@ class Table:
     def take_offsets(self, offsets: list[int]) -> TakeQuery: ...
     def take_row_ids(self, row_ids: list[int]) -> TakeQuery: ...
     async def blob_columns(self) -> list[str]: ...
+    async def add_bases(self, bases: list[Any]) -> None: ...
+    async def list_bases(self) -> list[tuple[str, Optional[str], bool]]: ...
     async def fetch_blobs(
         self, column: str, row_ids: list[int]
     ) -> pa.LargeBinaryArray: ...
@@ -649,9 +663,10 @@ class LsmWriteSpec:
     def identity(column: str) -> "LsmWriteSpec": ...
     @staticmethod
     def unsharded() -> "LsmWriteSpec": ...
-    def with_maintained_indexes(self, indexes: List[str]) -> "LsmWriteSpec":
-        """Return a copy of this spec asking the MemWAL to keep the named
-        indexes up to date as rows are appended."""
+    def with_maintained_indexes(self, indexes: Optional[List[str]]) -> "LsmWriteSpec":
+        """Set which indexes the MemWAL keeps up to date. None resolves every
+        index on the table at install, failing if one cannot be maintained;
+        a list is verbatim, empty means none."""
         ...
     def with_writer_config_defaults(self, defaults: Dict[str, str]) -> "LsmWriteSpec":
         """Return a copy of this spec recording the given default
@@ -666,13 +681,19 @@ class LsmWriteSpec:
     @property
     def num_buckets(self) -> Optional[int]: ...
     @property
-    def maintained_indexes(self) -> List[str]: ...
+    def maintained_indexes(self) -> Optional[List[str]]:
+        """Indexes the MemWAL keeps up to date, or None for every supported one."""
+        ...
     @property
     def writer_config_defaults(self) -> Dict[str, str]: ...
 
 class AddColumnsResult:
     version: int
 
+class RefreshColumnResult:
+    rows_filled: int
+    version: int
+
 class AlterColumnsResult:
     version: int
 

python/python/lancedb/db.py

@@ -524,6 +524,12 @@ class DBConnection(EnforceOverrides):
             namespace_path = []
         raise NotImplementedError
 
+    def drop_table_async(
+        self, name: str, namespace_path: Optional[List[str]] = None
+    ) -> Job:
+        """Start dropping a table and return its cleanup job."""
+        raise NotImplementedError
+
     def rename_table(
         self,
         cur_name: str,
@@ -804,7 +810,7 @@ class LanceDBConnection(DBConnection):
                 "manifest_enabled": self._manifest_enabled,
                 "namespace_client_properties": self._namespace_client_properties,
                 "read_consistency_interval_seconds": (
-                    rci.total_seconds() if rci is not None else None
+                    rci.total_seconds() if rci else None
                 ),
             }
         )
@@ -1186,6 +1192,20 @@ class LanceDBConnection(DBConnection):
             )
         )
 
+    @override
+    def drop_table_async(
+        self, name: str, namespace_path: Optional[List[str]] = None
+    ) -> Job:
+        """Start dropping a table and return its cleanup job.
+
+        The table may become unavailable before its data files are removed.
+        Call :meth:`Job.wait` to wait for cleanup to finish.
+        """
+        if namespace_path is None:
+            namespace_path = []
+        job = LOOP.run(self._conn.drop_table_async(name, namespace_path=namespace_path))
+        return Job(job if isinstance(job, AsyncJob) else AsyncJob(job))
+
     @override
     def drop_all_tables(self, namespace_path: Optional[List[str]] = None):
         if namespace_path is None:
@@ -1963,6 +1983,23 @@ class AsyncConnection(object):
             if f"Table '{name}' was not found" not in str(e):
                 raise e
 
+    async def drop_table_async(
+        self,
+        name: str,
+        *,
+        namespace_path: Optional[List[str]] = None,
+    ) -> AsyncJob:
+        """Start dropping a table and return its cleanup job.
+
+        The table may become unavailable before its data files are removed.
+        Await :meth:`AsyncJob.wait` to wait for cleanup to finish.
+        """
+        if namespace_path is None:
+            namespace_path = []
+        return AsyncJob(
+            await self._inner.drop_table_async(name, namespace_path=namespace_path)
+        )
+
     async def drop_all_tables(self, namespace_path: Optional[List[str]] = None):
         """Drop all tables from the database.
 

python/python/lancedb/embeddings/jinaai.py

@@ -87,12 +87,13 @@ class JinaEmbeddings(EmbeddingFunction):
         if isinstance(image, bytes):
             image_dict = {"image": base64.b64encode(image).decode("utf-8")}
         elif isinstance(image, (str, Path)):
-            parsed = urlparse.urlparse(image)
-            # TODO handle drive letter on windows.
+            parsed = urlparse(str(image))
             PIL_Image = attempt_import_or_raise("PIL.Image", "pillow")
             if parsed.scheme == "file":
                 pil_image = PIL_Image.open(parsed.path)
-            elif parsed.scheme == "":
+            elif parsed.scheme == "" or (os.name == "nt" and len(parsed.scheme) == 1):
+                # A Windows drive letter parses as a one-character scheme
+                # ("C:\\img.png" -> scheme="c"), so treat it as a local path.
                 pil_image = PIL_Image.open(image if os.name == "nt" else parsed.path)
             elif parsed.scheme.startswith("http"):
                 pil_image = PIL_Image.open(io.BytesIO(url_retrieve(image)))

python/python/lancedb/namespace.py

@@ -49,6 +49,7 @@ from lancedb._lancedb import (
 )
 from lancedb.background_loop import LOOP
 from lancedb.db import AsyncConnection, DBConnection
+from lancedb.job import AsyncJob, Job
 from lance_namespace import (
     LanceNamespace,
     connect as namespace_connect,
@@ -482,16 +483,6 @@ class LanceNamespaceDBConnection(DBConnection):
     def serialize(self) -> str:
         import json
 
-        if (
-            self._namespace_client_impl is None
-            or self._namespace_client_properties is None
-        ):
-            raise ValueError(
-                "Cannot serialize a namespace connection constructed from an "
-                "opaque namespace client. Pass namespace_client_impl and "
-                "namespace_client_properties when constructing the connection."
-            )
-
         return json.dumps(
             {
                 "connection_type": "namespace",
@@ -503,7 +494,7 @@ class LanceNamespaceDBConnection(DBConnection):
                 "storage_options": self.storage_options or None,
                 "read_consistency_interval_seconds": (
                     self.read_consistency_interval.total_seconds()
-                    if self.read_consistency_interval is not None
+                    if self.read_consistency_interval
                     else None
                 ),
             }
@@ -579,7 +570,6 @@ class LanceNamespaceDBConnection(DBConnection):
             self,
             name,
             namespace_path=namespace_path,
-            storage_options=storage_options,
             namespace_client=self._namespace_client,
             pushdown_operations=self._namespace_client_pushdown_operations,
             route_pushdown_to_rust=self._route_pushdown_to_rust,
@@ -618,8 +608,6 @@ class LanceNamespaceDBConnection(DBConnection):
             self,
             name,
             namespace_path=namespace_path,
-            storage_options=storage_options,
-            index_cache_size=index_cache_size,
             namespace_client=self._namespace_client,
             pushdown_operations=self._namespace_client_pushdown_operations,
             route_pushdown_to_rust=self._route_pushdown_to_rust,
@@ -637,6 +625,18 @@ class LanceNamespaceDBConnection(DBConnection):
             namespace_path = []
         LOOP.run(self._inner.drop_table(name, namespace_path=namespace_path))
 
+    @override
+    def drop_table_async(
+        self, name: str, namespace_path: Optional[List[str]] = None
+    ) -> Job:
+        """Start dropping a table and return its cleanup job."""
+        if namespace_path is None:
+            namespace_path = []
+        job = LOOP.run(
+            self._inner.drop_table_async(name, namespace_path=namespace_path)
+        )
+        return Job(job if isinstance(job, AsyncJob) else AsyncJob(job))
+
     @override
     def rename_table(
         self,
@@ -912,13 +912,10 @@ class LanceNamespaceDBConnection(DBConnection):
             self,
             name,
             namespace_path=namespace_path,
-            storage_options=storage_options,
-            index_cache_size=index_cache_size,
             location=table_uri,
             namespace_client=namespace_client,
             managed_versioning=managed_versioning,
             pushdown_operations=self._namespace_client_pushdown_operations,
-            route_pushdown_to_rust=self._route_pushdown_to_rust,
             _async=async_table,
         )
 
@@ -1150,6 +1147,14 @@ class AsyncLanceNamespaceDBConnection:
             namespace_path = []
         await self._inner.drop_table(name, namespace_path=namespace_path)
 
+    async def drop_table_async(
+        self, name: str, namespace_path: Optional[List[str]] = None
+    ) -> AsyncJob:
+        """Start dropping a table and return its cleanup job."""
+        if namespace_path is None:
+            namespace_path = []
+        return await self._inner.drop_table_async(name, namespace_path=namespace_path)
+
     async def rename_table(
         self,
         cur_name: str,

python/python/lancedb/permutation.py

@@ -591,13 +591,6 @@ class Permutation:
         then the first split will be used.
         """
         assert base_table is not None, "base_table is required"
-        # A PyTorch fork worker may construct its Permutation lazily from a
-        # table opened in the parent process. Reopen that table before the
-        # Rust reader clones its object-store clients and connection pools.
-        if hasattr(base_table, "_ensure_open"):
-            base_table._ensure_open()
-        if permutation_table is not None and hasattr(permutation_table, "_ensure_open"):
-            permutation_table._ensure_open()
         if split is not None:
             if permutation_table is None:
                 raise ValueError(

python/python/lancedb/py.typed

@@ -0,0 +1 @@
+

python/python/lancedb/pydantic.py

@@ -153,6 +153,16 @@ def Vector(
     return FixedSizeList
 
 
+def _raise_bare_vector_error(*_args):
+    raise TypeError("Vector must be parameterized with a dimension, e.g. Vector(128).")
+
+
+# Pydantic v1 and v2 otherwise treat the bare Vector factory as a field validator
+# and inspect its signature, which produces misleading errors about internal types.
+setattr(Vector, "__get_validators__", _raise_bare_vector_error)
+setattr(Vector, "__get_pydantic_core_schema__", _raise_bare_vector_error)
+
+
 def MultiVector(
     dim: int, value_type: pa.DataType = pa.float32(), nullable: bool = True
 ) -> Type:

python/python/lancedb/remote/db.py

@@ -23,7 +23,7 @@ import pyarrow as pa
 
 from ..common import DATA
 from ..db import DBConnection, LOOP
-from ..job import Job
+from ..job import AsyncJob, Job
 
 if TYPE_CHECKING:
     from .._lancedb import JobDescription, JobInfo
@@ -663,6 +663,16 @@ class RemoteDBConnection(DBConnection):
             namespace_path = []
         LOOP.run(self._conn.drop_table(name, namespace_path=namespace_path))
 
+    @override
+    def drop_table_async(
+        self, name: str, namespace_path: Optional[List[str]] = None
+    ) -> Job:
+        """Start dropping a table and return its cleanup job."""
+        if namespace_path is None:
+            namespace_path = []
+        job = LOOP.run(self._conn.drop_table_async(name, namespace_path=namespace_path))
+        return Job(job if isinstance(job, AsyncJob) else AsyncJob(job))
+
     @override
     def rename_table(
         self,

python/python/lancedb/remote/table.py

@@ -50,7 +50,7 @@ from lancedb.index import (
 )
 from lancedb.job import Job
 from lancedb.remote.db import LOOP
-from lancedb.table import IndexConfigType, KNOWN_METRICS
+from lancedb.table import IndexConfigType, KNOWN_METRICS, TableBase
 import pyarrow as pa
 
 from lancedb.common import DATA, VEC, VECTOR_COLUMN_NAME
@@ -958,8 +958,19 @@ class RemoteTable(Table):
     def count_rows(self, filter: Optional[str] = None) -> int:
         return LOOP.run(self._table.count_rows(filter))
 
-    def add_columns(self, transforms: Dict[str, str]) -> AddColumnsResult:
-        return LOOP.run(self._table.add_columns(transforms))
+    def add_columns(
+        self,
+        transforms: Dict[str, str] | None = None,
+        *,
+        computed: Dict[str, str] | None = None,
+    ) -> AddColumnsResult:
+        return LOOP.run(self._table.add_columns(transforms, computed=computed))
+
+    def refresh_column(self, column: str):
+        return LOOP.run(self._table.refresh_column(column))
+
+    def refresh_column_async(self, column: str) -> Job:
+        return Job(LOOP.run(self._table.refresh_column_async(column)))
 
     def alter_columns(
         self, *alterations: Iterable[Dict[str, str]]
@@ -1071,6 +1082,17 @@ class RemoteTable(Table):
     def blob_columns(self) -> list[str]:
         return LOOP.run(self._table.blob_columns())
 
+    def add_bases(
+        self,
+        bases: Union[str, TableBase, Iterable[Union[str, TableBase]]],
+    ) -> None:
+        """Register additional storage bases for this table."""
+        LOOP.run(self._table.add_bases(bases))
+
+    def list_bases(self) -> list[TableBase]:
+        """Return the additional storage bases for the current table snapshot."""
+        return LOOP.run(self._table.list_bases())
+
     def fetch_blobs(
         self, column: str, row_ids: Union[list[int], pa.Table]
     ) -> pa.LargeBinaryArray:

python/python/lancedb/streaming.py

@@ -11,6 +11,11 @@ Provides StreamingDataset, a PyTorch IterableDataset that guarantees:
 - **Resumability**: state_dict / load_state_dict capture per-split consumption
   counts so training can resume from an exact mid-epoch position even when the
   distributed topology changes between runs.
+
+Transform failures on bad rows (e.g. nulls or NaNs from incomplete data) can
+be tolerated with ``on_transform_error="skip"``; see the parameter
+documentation on StreamingDataset for how this interacts with the guarantees
+above.
 """
 
 import ctypes
@@ -22,7 +27,7 @@ import time
 from collections import deque
 from concurrent.futures import ThreadPoolExecutor
 from multiprocessing import RawArray
-from typing import Any, Callable, Iterator, Optional
+from typing import Any, Callable, Iterator, Optional, Union
 
 from torch.utils.data import IterableDataset, get_worker_info
 
@@ -127,6 +132,49 @@ class StreamingDataset(IterableDataset):
         Maximum number of transforms to run concurrently.  Must be greater
         than zero.  When ``None`` (the default), uses ``os.cpu_count()`` or 1
         when the CPU count is unavailable.
+    on_transform_error:
+        What to do when the transform raises an exception:
+
+        - ``"raise"`` (the default): the exception propagates and iteration
+          aborts.
+        - ``"skip"``: the failing rows are dropped and iteration continues.
+        - ``"warn"``: like ``"skip"``, but a warning is logged for each
+          failing batch.
+        - a callable ``handler(exc) -> bool``: called with the exception;
+          return ``True`` to skip the failing rows or ``False`` to re-raise.
+          Useful to skip only expected error types (compatible with
+          ``webdataset.handlers`` style handlers).
+
+        When a batch fails, the transform is re-invoked on each single-row
+        slice of the batch so that only the rows that actually fail are
+        dropped.  Transforms should therefore be deterministic and accept
+        batches of any size (including one row).  Skipped rows are counted in
+        ``rows_skipped``.
+
+        Skipping weakens the elastic-determinism guarantee at the end of the
+        epoch: splits that lose more rows than others run dry earlier, and
+        each rank's iterator ends at the last cycle where every split *it
+        owns* still has a row.  Because bad rows are not distributed evenly
+        across splits, this means one rank's iterator can yield noticeably
+        fewer or more steps than another rank's *in the same run* — there is
+        no cross-rank coordination that stops every rank at the same global
+        step.  This is generally safe for asynchronous or single-rank use,
+        but synchronous distributed training (e.g. ranks that call
+        ``all_reduce`` every step) can hang or deadlock if one rank's
+        iterator is exhausted while others are still stepping; callers doing
+        synchronous multi-rank training with ``on_transform_error != "raise"``
+        are responsible for their own cross-rank stopping mechanism (e.g.
+        broadcasting a stop signal on ``StopIteration``).  The final few
+        global steps can also differ across topologies (bounded by the skew
+        in bad-row counts across splits).  The sequence of samples yielded
+        from each split remains deterministic.  Mid-epoch
+        checkpoints remain exact provided the transform fails
+        deterministically; in multi-rank training each rank must save its
+        own ``state_dict`` and the states must be combined with
+        ``merge_state_dicts`` before resuming on a different topology.
+        Prefer the ``filter`` parameter when bad rows can be expressed as a
+        SQL predicate (e.g. ``"col IS NOT NULL"``) — filtering happens before
+        splits are built, so every guarantee is fully preserved.
     worker_info_override:
         If set, used in place of ``torch.utils.data.get_worker_info()`` to
         determine the DataLoader worker assignment.  Intended for unit tests
@@ -152,6 +200,7 @@ class StreamingDataset(IterableDataset):
         filter: Optional[str] = None,
         transform: Optional[Callable] = None,
         transform_parallelism: Optional[int] = None,
+        on_transform_error: Union[str, Callable[[Exception], bool]] = "raise",
         connection_factory: Optional[Callable[[str], Any]] = None,
         worker_info_override=None,
     ):
@@ -167,6 +216,13 @@ class StreamingDataset(IterableDataset):
             )
         if transform_parallelism is not None and transform_parallelism <= 0:
             raise ValueError("transform_parallelism must be greater than 0")
+        if on_transform_error not in ("raise", "skip", "warn") and not callable(
+            on_transform_error
+        ):
+            raise ValueError(
+                "on_transform_error must be 'raise', 'skip', 'warn', or a "
+                f"callable, got {on_transform_error!r}"
+            )
 
         self._table = table
         self._num_splits = num_splits
@@ -182,6 +238,7 @@ class StreamingDataset(IterableDataset):
         self._filter = filter
         self._transform = transform
         self._transform_parallelism = transform_parallelism
+        self._on_transform_error = on_transform_error
         self._connection_factory = connection_factory
         self._worker_info_override = worker_info_override
 
@@ -199,19 +256,28 @@ class StreamingDataset(IterableDataset):
         # in the main process.  RawArray is picklable via the forkserver
         # reduction protocol so it survives the dataset pickle round-trip.
         # Layout: [unscanned_rows, raw_rows, cooked_rows, consumed_rows,
-        #          bytes_loaded, fetch_time_us, transform_time_us]
-        self._worker_stats: RawArray = RawArray(ctypes.c_int64, 7)
+        #          bytes_loaded, fetch_time_us, transform_time_us,
+        #          rows_skipped]
+        self._worker_stats: RawArray = RawArray(ctypes.c_int64, 8)
 
         # Cumulative bytes of Arrow buffer data fetched across all iterations.
         self._bytes_loaded: int = 0
         # Cumulative seconds spent in LanceDB I/O and in transform functions.
         self._fetch_time: float = 0.0
         self._transform_time: float = 0.0
+        # Cumulative rows dropped by on_transform_error across all iterations.
+        self._rows_skipped: int = 0
 
         # Number of samples each split has already been consumed.  At global
         # step boundaries all splits have consumed this many samples, so a
         # single scalar captures the topology-independent checkpoint state.
         self._resume_offset: int = 0
+        # Permutation position each split has consumed through, keyed by
+        # global split index.  Equal to _resume_offset for every split unless
+        # on_transform_error skipped rows, in which case skipped positions
+        # push the watermark of the affected splits further ahead.  Splits
+        # this instance has never iterated have no entry.
+        self._resume_positions: dict[int, int] = {}
 
         # Build the permutation table once, deterministically.
         builder = permutation_builder(table)
@@ -275,6 +341,7 @@ class StreamingDataset(IterableDataset):
         # Set identity transform on each Permutation so __getitems__ returns
         # the raw RecordBatch.  Stage 2 applies the real transform.
         permutations: list[Permutation] = []
+        initial_positions: list[int] = []
         for split_idx in my_splits:
             perm = Permutation.from_tables(
                 self._table, self._perm_table, split=split_idx
@@ -282,14 +349,20 @@ class StreamingDataset(IterableDataset):
             if self._columns is not None:
                 perm = perm.select_columns(self._columns)
             perm = perm.with_transform(lambda batch: batch)
-            if self._resume_offset > 0:
-                perm = perm.with_skip(self._resume_offset)
+            start_pos = self._resume_positions.get(split_idx, self._resume_offset)
+            if start_pos > 0:
+                perm = perm.with_skip(start_pos)
+            initial_positions.append(start_pos)
             permutations.append(perm)
 
         n = len(permutations)
         split_sizes = [perm.num_rows for perm in permutations]
         initial_offset = self._resume_offset
         local_consumed = [0] * n
+        # Permutation position each split has consumed through (absolute,
+        # i.e. counted from the start of the unskipped split).  Runs ahead of
+        # initial + local_consumed when rows are skipped.
+        pos_consumed = list(initial_positions)
 
         batch_size = self._read_batch_size
         max_prefetch = self._prefetch_batches
@@ -302,12 +375,14 @@ class StreamingDataset(IterableDataset):
             self._transform if self._transform is not None else Transforms.arrow2python
         )
 
-        # Per-split pipeline state.
+        # Per-split pipeline state.  Batches are paired with the absolute
+        # permutation position of their first row so that skipped rows can be
+        # accounted for in pos_consumed.
         fetch_head = [0] * n
-        io_pending = [deque() for _ in range(n)]  # Future[RecordBatch]
-        raw_batches = [deque() for _ in range(n)]  # RecordBatch — fetched, awaiting tx
-        tx_pending = [deque() for _ in range(n)]  # Future[list[Any]]
-        cooked = [deque() for _ in range(n)]  # rows ready to yield
+        io_pending = [deque() for _ in range(n)]  # (abs_start, Future[RecordBatch])
+        raw_batches = [deque() for _ in range(n)]  # (abs_start, RecordBatch)
+        tx_pending = [deque() for _ in range(n)]  # Future[list[(abs_pos, row)]]
+        cooked = [deque() for _ in range(n)]  # (abs_pos, row) ready to yield
 
         # Limit simultaneous transforms to transform_workers across all splits.
         tx_semaphore = threading.Semaphore(transform_workers)
@@ -330,7 +405,8 @@ class StreamingDataset(IterableDataset):
             fetch_head[i] += fetch
             perm_i = permutations[i]
             indices = list(range(start, start + fetch))
-            io_pending[i].append(io_pool.submit(_io_call, perm_i, indices))
+            abs_start = initial_positions[i] + start
+            io_pending[i].append((abs_start, io_pool.submit(_io_call, perm_i, indices)))
 
         def _fill_io(i: int) -> None:
             while len(io_pending[i]) < max_prefetch and fetch_head[i] < split_sizes[i]:
@@ -338,15 +414,72 @@ class StreamingDataset(IterableDataset):
 
         def _drain_io(i: int) -> None:
             """Move completed I/O futures into raw_batches non-blockingly."""
-            while io_pending[i] and io_pending[i][0].done():
-                raw_batches[i].append(io_pending[i].popleft().result())
+            while io_pending[i] and io_pending[i][0][1].done():
+                abs_start, fut = io_pending[i].popleft()
+                raw_batches[i].append((abs_start, fut.result()))
 
         # ── Stage 2 helpers ───────────────────────────────────────────────────
 
-        def _tx_call_guarded(batch):
+        on_error = self._on_transform_error
+
+        def _should_skip(exc: Exception) -> bool:
+            if on_error == "raise":
+                return False
+            if callable(on_error):
+                return bool(on_error(exc))
+            return True  # "skip" or "warn"
+
+        def _check_row_count(rows: list, num_rows: int) -> None:
+            if len(rows) != num_rows:
+                raise ValueError(
+                    f"transform returned {len(rows)} rows for a batch of "
+                    f"{num_rows}; transforms must return exactly one output "
+                    "row per input row.  To drop bad rows, raise inside the "
+                    "transform and pass on_transform_error='skip'."
+                )
+
+        def _transform_isolated(abs_start, batch, batch_exc):
+            """Re-run the transform on single-row slices, dropping failures."""
+            out = []
+            skipped = 0
+            first_exc = None
+            for j in range(batch.num_rows):
+                try:
+                    rows = list(final_transform(batch.slice(j, 1)))
+                except Exception as exc:
+                    if not _should_skip(exc):
+                        raise
+                    skipped += 1
+                    if first_exc is None:
+                        first_exc = exc
+                    continue
+                _check_row_count(rows, 1)
+                out.append((abs_start + j, rows[0]))
+            self._rows_skipped += skipped
+            if skipped and on_error == "warn":
+                logger.warning(
+                    "Skipped %d of %d rows whose transform failed (first error: %r)",
+                    skipped,
+                    batch.num_rows,
+                    first_exc if first_exc is not None else batch_exc,
+                )
+            return out
+
+        def _transform_batch(abs_start, batch):
+            """Apply the transform, returning [(abs_pos, row), ...]."""
+            try:
+                rows = list(final_transform(batch))
+            except Exception as exc:
+                if not _should_skip(exc):
+                    raise
+                return _transform_isolated(abs_start, batch, exc)
+            _check_row_count(rows, batch.num_rows)
+            return [(abs_start + j, row) for j, row in enumerate(rows)]
+
+        def _tx_call_guarded(abs_start, batch):
             try:
                 t0 = time.perf_counter()
-                result = final_transform(batch)
+                result = _transform_batch(abs_start, batch)
                 self._transform_time += time.perf_counter() - t0
                 return result
             finally:
@@ -355,8 +488,8 @@ class StreamingDataset(IterableDataset):
         def _try_submit_tx(i: int) -> None:
             """Submit transforms for raw_batches[i] up to available capacity."""
             while raw_batches[i] and tx_semaphore.acquire(blocking=False):
-                batch = raw_batches[i].popleft()
-                tx_pending[i].append(tx_pool.submit(_tx_call_guarded, batch))
+                abs_start, batch = raw_batches[i].popleft()
+                tx_pending[i].append(tx_pool.submit(_tx_call_guarded, abs_start, batch))
 
         def _drain_tx(i: int) -> None:
             """Move completed transform futures into cooked non-blockingly."""
@@ -384,11 +517,14 @@ class StreamingDataset(IterableDataset):
                     # Acquire a transform slot (may block briefly if all
                     # transform_workers are busy with other splits).
                     tx_semaphore.acquire()
-                    batch = raw_batches[i].popleft()
-                    tx_pending[i].append(tx_pool.submit(_tx_call_guarded, batch))
+                    abs_start, batch = raw_batches[i].popleft()
+                    tx_pending[i].append(
+                        tx_pool.submit(_tx_call_guarded, abs_start, batch)
+                    )
                 elif io_pending[i]:
                     # Block on the oldest in-flight I/O fetch.
-                    raw_batches[i].append(io_pending[i].popleft().result())
+                    abs_start, fut = io_pending[i].popleft()
+                    raw_batches[i].append((abs_start, fut.result()))
                     _advance(i)
                 else:
                     break  # split exhausted
@@ -407,15 +543,28 @@ class StreamingDataset(IterableDataset):
                         _fill_io(i)
 
                     while True:
-                        # Stop when any split is exhausted (all exhaust
-                        # simultaneously: equal split sizes + round-robin).
-                        if any(local_consumed[i] >= split_sizes[i] for i in range(n)):
+                        # A cycle only runs if every split can still produce a
+                        # row.  Without skips all splits exhaust simultaneously
+                        # (equal split sizes + round-robin); when
+                        # on_transform_error drops rows a split can run dry
+                        # early, ending the epoch at the last complete cycle.
+                        # This check only sees splits owned by this rank/worker
+                        # (my_splits) — there is no cross-rank coordination, so
+                        # a different rank with fewer skipped rows keeps going;
+                        # see the on_transform_error docstring.
+                        exhausted = False
+                        for i in range(n):
+                            _ensure_cooked(i)
+                            if not cooked[i]:
+                                exhausted = True
+                                break
+                        if exhausted:
                             break
 
                         for i in range(n):
-                            _ensure_cooked(i)
-                            row = cooked[i].popleft()
+                            pos, row = cooked[i].popleft()
                             local_consumed[i] += 1
+                            pos_consumed[i] = pos + 1
                             _advance(i)
 
                             # After the last split in each cycle: update the
@@ -424,21 +573,39 @@ class StreamingDataset(IterableDataset):
                             # even when __iter__ runs in a worker process.
                             if i == n - 1:
                                 self._resume_offset = initial_offset + local_consumed[i]
+                                for j, split_idx in enumerate(my_splits):
+                                    self._resume_positions[split_idx] = pos_consumed[j]
                                 ws = self._worker_stats
                                 ws[0] = sum(
                                     split_sizes[j] - fetch_head[j] for j in range(n)
                                 )
                                 ws[1] = sum(
-                                    batch.num_rows for q in raw_batches for batch in q
+                                    batch.num_rows
+                                    for q in raw_batches
+                                    for _, batch in q
                                 )
                                 ws[2] = sum(len(q) for q in cooked)
                                 ws[3] = sum(local_consumed)
                                 ws[4] = self._bytes_loaded
                                 ws[5] = int(self._fetch_time * 1_000_000)
                                 ws[6] = int(self._transform_time * 1_000_000)
+                                ws[7] = self._rows_skipped
 
                             yield row
                 finally:
+                    # Final stats flush: the per-cycle write above never runs
+                    # when iteration ends mid-cycle (e.g. a split whose rows
+                    # were all skipped before completing a single cycle), so
+                    # counters like rows_skipped would otherwise be stale.
+                    ws = self._worker_stats
+                    ws[0] = sum(split_sizes[j] - fetch_head[j] for j in range(n))
+                    ws[1] = 0  # queue-depth properties document 0 when idle
+                    ws[2] = 0
+                    ws[3] = sum(local_consumed)
+                    ws[4] = self._bytes_loaded
+                    ws[5] = int(self._fetch_time * 1_000_000)
+                    ws[6] = int(self._transform_time * 1_000_000)
+                    ws[7] = self._rows_skipped
                     self._raw_batches_ref = None
                     self._cooked_ref = None
                     self._fetch_head_ref = None
@@ -492,7 +659,7 @@ class StreamingDataset(IterableDataset):
         batches.  Returns 0 when not iterating.
         """
         if self._raw_batches_ref is not None:
-            return sum(batch.num_rows for q in self._raw_batches_ref for batch in q)
+            return sum(batch.num_rows for q in self._raw_batches_ref for _, batch in q)
         return int(self._worker_stats[1])
 
     @property
@@ -522,6 +689,19 @@ class StreamingDataset(IterableDataset):
             )
         return int(self._worker_stats[0])
 
+    @property
+    def rows_skipped(self) -> int:
+        """Number of rows dropped because their transform raised an exception.
+
+        Only ever non-zero when ``on_transform_error`` is set to ``"skip"``,
+        ``"warn"``, or a callable that returned ``True``.  Accumulates across
+        multiple iterations of the same dataset instance and is never reset
+        automatically.
+        """
+        if self._raw_batches_ref is not None:
+            return self._rows_skipped
+        return int(self._worker_stats[7])
+
     @property
     def consumed_rows(self) -> int:
         """Number of rows already yielded to the caller across all splits.
@@ -587,12 +767,27 @@ class StreamingDataset(IterableDataset):
         every split has been consumed the same number of times (by the
         round-robin design), so the per-split count is a single uniform value
         that is identical across all ranks and DataLoader workers.
+
+        ``positions_consumed_per_split`` records how far into each split's
+        permutation iteration has advanced.  It only differs from
+        ``samples_consumed_per_split`` when ``on_transform_error`` skipped
+        rows, in which case entries are exact for the splits this instance
+        iterated and a lower bound (the sample count) for splits owned by
+        other ranks or workers.  Combine the state dicts from all ranks with
+        [merge_state_dicts][lancedb.streaming.StreamingDataset.merge_state_dicts]
+        to recover the exact value for every split before resuming on a
+        different topology.
         """
+        positions = [
+            self._resume_positions.get(split, self._resume_offset)
+            for split in range(self._num_splits)
+        ]
         return {
             "shuffle_seed": self._shuffle_seed,
             "num_splits": self._num_splits,
             "epoch": self._epoch,
             "samples_consumed_per_split": [self._resume_offset] * self._num_splits,
+            "positions_consumed_per_split": positions,
         }
 
     def load_state_dict(self, state: dict) -> None:
@@ -618,3 +813,96 @@ class StreamingDataset(IterableDataset):
             self._resume_offset = consumed[0] if consumed else 0
         else:
             self._resume_offset = int(consumed)
+        # Older checkpoints predate positions_consumed_per_split; without
+        # skipped rows positions equal sample counts, so falling back to
+        # _resume_offset (the .get default in __iter__) is exact.
+        positions = state.get("positions_consumed_per_split")
+        if positions is None:
+            self._resume_positions = {}
+        else:
+            self._resume_positions = {
+                split: int(pos) for split, pos in enumerate(positions)
+            }
+
+    @staticmethod
+    def merge_state_dicts(states: list[dict]) -> dict:
+        """Merge state dicts saved by different ranks into one exact state.
+
+        Only needed when ``on_transform_error`` skips rows in multi-rank
+        training: each rank then knows the exact permutation position only for
+        its own splits, and records a lower bound for the rest.  Because
+        exactly one rank owns each split, the elementwise maximum across all
+        ranks' ``positions_consumed_per_split`` recovers the exact position of
+        every split.  Without skipped rows every rank's state is already
+        identical and merging is a no-op.
+
+        Raises ``ValueError`` if the states are empty or were not produced by
+        the same run (mismatched seed, split count, epoch, or sample counts).
+
+        The merge is always all-to-all and topology-agnostic: collect the
+        ``state_dict()`` from every rank of the *previous* run into one list,
+        merge that whole list, and hand the identical merged result to every
+        rank of the *next* run — regardless of whether the rank count grew,
+        shrank, or stayed the same. There is no pairwise or subset merging
+        step, because each split's exact position is only known to whichever
+        rank owned that split, and the elementwise maximum needs every rank's
+        contribution to be correct.
+
+        For example, checkpointing 8 ranks and resuming on 4 (the same
+        pattern applies when growing, e.g. 4 ranks resuming on 8)::
+
+            states = [ds.state_dict() for ds in previous_run_datasets]  # 8
+            merged = StreamingDataset.merge_state_dicts(states)
+            for ds in resumed_datasets:  # now only 4 ranks
+                ds.load_state_dict(merged)  # same dict on every rank
+
+        The rank count on either side never affects the merge itself, since
+        ``merge_state_dicts`` only cares about the list of states it is
+        given.  Each split's position is recovered by elementwise maximum;
+        here rank 0 owned split 0 (and skipped two rows there) while rank 1
+        owned split 1 (and skipped one row):
+
+        >>> rank0 = {
+        ...     "shuffle_seed": 0, "num_splits": 2, "epoch": 0,
+        ...     "samples_consumed_per_split": [3, 3],
+        ...     "positions_consumed_per_split": [5, 3],
+        ... }
+        >>> rank1 = {
+        ...     "shuffle_seed": 0, "num_splits": 2, "epoch": 0,
+        ...     "samples_consumed_per_split": [3, 3],
+        ...     "positions_consumed_per_split": [3, 4],
+        ... }
+        >>> merged = StreamingDataset.merge_state_dicts([rank0, rank1])
+        >>> merged["positions_consumed_per_split"]
+        [5, 4]
+        """
+        if not states:
+            raise ValueError("merge_state_dicts requires at least one state dict")
+        first = states[0]
+        for state in states[1:]:
+            for key in ("shuffle_seed", "num_splits", "epoch"):
+                if state[key] != first[key]:
+                    raise ValueError(
+                        f"{key} mismatch across state dicts: "
+                        f"{state[key]} != {first[key]}"
+                    )
+            if (
+                state["samples_consumed_per_split"]
+                != first["samples_consumed_per_split"]
+            ):
+                raise ValueError(
+                    "samples_consumed_per_split mismatch across state dicts; "
+                    "state_dict() must be called at the same global step "
+                    "boundary on every rank"
+                )
+        merged = dict(first)
+        all_positions = [
+            state.get(
+                "positions_consumed_per_split", state["samples_consumed_per_split"]
+            )
+            for state in states
+        ]
+        merged["positions_consumed_per_split"] = [
+            max(per_split) for per_split in zip(*all_positions)
+        ]
+        return merged

python/python/lancedb/table.py

@@ -6,8 +6,6 @@ from __future__ import annotations
 import asyncio
 import inspect
 import deprecation
-import os
-import threading
 import warnings
 from abc import ABC, abstractmethod
 from dataclasses import dataclass
@@ -21,6 +19,7 @@ from typing import (
     Iterable,
     List,
     Literal,
+    Mapping,
     Optional,
     Sequence,
     Tuple,
@@ -110,6 +109,11 @@ def _should_push_down_query_table(
     return namespace_client is not None and "QueryTable" in pushdown_operations
 
 
+def _polars_predicate_pushdown_barrier(frame: Any) -> Any:
+    """Return a Polars frame unchanged while blocking predicate pushdown."""
+    return frame
+
+
 _MODEL_BACKED_TOKENIZER_PREFIXES = ("jieba", "lindera")
 _MODEL_BACKED_TOKENIZER_ERRORS = (
     "unknown base tokenizer",
@@ -165,7 +169,7 @@ def _maybe_add_fts_error_note(
 
 
 if TYPE_CHECKING:
-    from .db import DBConnection, LanceDBConnection
+    from .db import LanceDBConnection
     from ._lancedb import (
         Table as LanceDBTable,
         OptimizeStats,
@@ -173,6 +177,7 @@ if TYPE_CHECKING:
         CompactionStats,
         Tag,
         AddColumnsResult,
+        RefreshColumnResult,
         AddResult,
         AlterColumnsResult,
         UpdateFieldMetadataResult,
@@ -706,6 +711,21 @@ def _normalize_progress(progress):
     return progress, False
 
 
+@dataclass
+class TableBase:
+    """An extra storage prefix registered on a table.
+
+    ``path`` is an object-store URI. ``name`` is an optional alias.
+    ``is_dataset_root`` is true when ``path`` points to a Lance dataset
+    root. When false, ``path`` points directly to the directory containing
+    the referenced files.
+    """
+
+    path: str
+    name: Optional[str] = None
+    is_dataset_root: bool = False
+
+
 class Table(ABC):
     """
     A Table is a collection of Records in a LanceDB Database.
@@ -866,12 +886,18 @@ class Table(ABC):
         """
         raise NotImplementedError
 
-    def to_polars(self, **kwargs) -> "pl.DataFrame":
-        """Return the table as a polars.DataFrame.
+    def to_polars(self, **kwargs) -> "pl.LazyFrame":
+        """Return the table as a Polars LazyFrame.
+
+        Note
+        ----
+        The Polars streaming engine is not supported because it does not currently
+        implement Python PyArrow dataset scans. Use the default engine when collecting
+        this LazyFrame.
 
         Returns
         -------
-        polars.DataFrame
+        polars.LazyFrame
         """
         raise NotImplementedError
 
@@ -1558,6 +1584,22 @@ class Table(ABC):
     def blob_columns(self) -> list[str]:
         """Names of the blob v2 columns declared on this table."""
 
+    def add_bases(
+        self,
+        bases: Union[str, TableBase, Iterable[Union[str, TableBase]]],
+    ) -> None:
+        """Register additional storage bases for this table.
+
+        A URI string is a non-root base with no alias::
+
+            table.add_bases("s3://bucket/media/")
+        """
+        raise NotImplementedError
+
+    def list_bases(self) -> list[TableBase]:
+        """Return the additional storage bases for the current table snapshot."""
+        raise NotImplementedError
+
     @abstractmethod
     def fetch_blobs(
         self, column: str, row_ids: Union[list[int], pa.Table]
@@ -1907,7 +1949,14 @@ class Table(ABC):
 
     @abstractmethod
     def add_columns(
-        self, transforms: Dict[str, str] | pa.Field | List[pa.Field] | pa.Schema
+        self,
+        transforms: Dict[str, str]
+        | pa.Field
+        | List[pa.Field]
+        | pa.Schema
+        | None = None,
+        *,
+        computed: Dict[str, str] | None = None,
     ):
         """
         Add new columns with defined values.
@@ -1921,11 +1970,95 @@ class Table(ABC):
             Alternatively, a pyarrow Field or Schema can be provided to add
             new columns with the specified data types. The new columns will
             be initialized with null values.
+        computed: Dict[str, str], optional
+            A map of column name to a SQL expression defining the column. The
+            column's type and inputs are derived from the expression, so no
+            data type is supplied.
+
+            Unlike ``transforms``, the expression is stored rather than
+            evaluated now: the column is committed with no values, and rows get
+            them from [`refresh_column`][lancedb.table.Table.refresh_column].
+            Declaring one therefore costs the same on a large table as on an
+            empty one.
+
+            A refresh does not revisit rows it has already filled, so mutating
+            an input leaves the value computed at fill time; recomputing means
+            dropping the column and declaring it again. While a declaration
+            reads a column, that column cannot be renamed, retyped or dropped.
+
+            On LanceDB Cloud and Enterprise the expression is planned by the
+            server, and the refresh runs as a server job -- see
+            [`refresh_column_async`][lancedb.table.Table.refresh_column_async].
+            Cannot be combined with ``transforms``.
 
         Returns
         -------
         AddColumnsResult
             version: the new version number of the table after adding columns.
+
+        Examples
+        --------
+        >>> import lancedb
+        >>> db = lancedb.connect("./.lancedb")
+        >>> table = db.create_table("computed_demo", [{"x": 1}, {"x": 2}])
+        >>> table.add_columns(computed={"doubled": "x * 2"})
+        AddColumnsResult(version=2)
+        >>> table.refresh_column("doubled")
+        RefreshColumnResult(rows_filled=2, version=3)
+        >>> table.to_arrow().sort_by("x").to_pandas()
+           x  doubled
+        0  1        2
+        1  2        4
+        """
+
+    @abstractmethod
+    def refresh_column(self, column: str) -> "RefreshColumnResult":
+        """
+        Fill the rows of a computed column that hold no value yet.
+
+        Declared with ``add_columns(computed=...)``, a column starts empty and
+        gets its values here. Rows appended since the last refresh are filled
+        by the next one; rows already filled are left as they are, so the call
+        is idempotent and does not observe a mutated input.
+
+        Local tables only: a remote refresh runs as a server job, through
+        [`refresh_column_async`][lancedb.table.Table.refresh_column_async].
+
+        Parameters
+        ----------
+        column: str
+            The name of the computed column to fill.
+
+        Returns
+        -------
+        RefreshColumnResult
+            rows_filled: the number of rows given a value.
+            version: the new version number of the table.
+        """
+
+    @abstractmethod
+    def refresh_column_async(self, column: str) -> Job:
+        """
+        Like :meth:`refresh_column`, but returns a handle to the refresh job
+        instead of blocking until it completes.
+
+        The job may already be complete when returned; callers must not assume
+        the column is filled until :meth:`Job.wait` returns. Invalid input --
+        an unknown column, or one that is not computed -- raises here rather
+        than failing the job. On local tables the job runs in-process; on
+        LanceDB Cloud and Enterprise it is the server's backfill job.
+
+        Examples
+        --------
+        >>> import lancedb
+        >>> db = lancedb.connect("./.lancedb")
+        >>> table = db.create_table("computed_job_demo", [{"x": 1}, {"x": 2}])
+        >>> table.add_columns(computed={"doubled": "x * 2"})
+        AddColumnsResult(version=2)
+        >>> job = table.refresh_column_async("doubled")
+        >>> job.wait()
+        >>> job.status()
+        'finished'
         """
 
     @abstractmethod
@@ -2107,23 +2240,6 @@ class Table(ABC):
         """
 
 
-@dataclass
-class _LanceTableReopenState:
-    """Process-independent coordinates for reopening a native table."""
-
-    connection_state: Optional[str]
-    can_reopen_after_fork: bool
-    fork_reopen_error: Optional[str]
-    name: str
-    namespace_path: List[str]
-    storage_options: Optional[Dict[str, str]]
-    index_cache_size: Optional[int]
-    location: Optional[str]
-    managed_versioning: Optional[bool]
-    branch: Optional[str]
-    checkout_version: Optional[int]
-
-
 class LanceTable(Table):
     """
     A table in a LanceDB database.
@@ -2158,10 +2274,7 @@ class LanceTable(Table):
             namespace_path = []
         self._conn = connection
         self._namespace_path = namespace_path
-        self._storage_options = storage_options
-        self._index_cache_size = index_cache_size
         self._location = location  # Store location for use in _dataset_path
-        self._managed_versioning = managed_versioning
         self._namespace_client = namespace_client
         self._pushdown_operations = pushdown_operations or set()
         # When the connection built the namespace client natively (e.g. an
@@ -2186,206 +2299,9 @@ class LanceTable(Table):
                     managed_versioning=managed_versioning,
                 )
             )
-        self._initialize_reopen_state(name)
-
-    def _initialize_reopen_state(self, name: str) -> None:
-        """Capture the state needed to replace inherited native handles."""
-        self._name = name
-        self._pid = os.getpid()
-        self._native_state_guard = (self._pid, threading.RLock())
-
-        # A native table owns object-store clients and connection pools. Those
-        # handles must not be used after fork, so retain a process-independent
-        # connection description while it is still safe to inspect the parent
-        # connection. Connections without reconstructible metadata are not
-        # safe to reuse in a forked child, so retain a clear diagnostic rather
-        # than advertising them as reopenable based on JSON encoding alone.
-        try:
-            connection_uri: Optional[str] = self._conn.uri
-        except Exception:
-            connection_uri = None
-
-        fork_reopen_error: Optional[str] = None
-        try:
-            connection_state: Optional[str] = self._conn.serialize()
-            can_reopen_after_fork = connection_uri is not None and not (
-                connection_uri.startswith("memory://")
-            )
-        except Exception as error:
-            connection_state = None
-            can_reopen_after_fork = False
-            if connection_uri is not None and not connection_uri.startswith(
-                "memory://"
-            ):
-                fork_reopen_error = (
-                    f"Cannot reopen table {name!r} in a forked process: {error}"
-                )
-
-        self._reopen_state = _LanceTableReopenState(
-            connection_state=connection_state,
-            can_reopen_after_fork=can_reopen_after_fork,
-            fork_reopen_error=fork_reopen_error,
-            name=name,
-            namespace_path=list(self._namespace_path),
-            storage_options=(
-                dict(self._storage_options)
-                if self._storage_options is not None
-                else None
-            ),
-            index_cache_size=self._index_cache_size,
-            location=self._location,
-            managed_versioning=self._managed_versioning,
-            branch=self._table.current_branch(),
-            checkout_version=None,
-        )
-
-    @property
-    def _connection_state(self) -> Optional[str]:
-        """Serialized connection retained for worker reconstruction."""
-        return self._reopen_state.connection_state
-
-    @property
-    def _can_reopen_after_fork(self) -> bool:
-        return self._reopen_state.can_reopen_after_fork
-
-    @property
-    def _branch(self) -> Optional[str]:
-        state = getattr(self, "_reopen_state", None)
-        if state is not None:
-            return state.branch
-        return getattr(self, "_legacy_branch", None)
-
-    @_branch.setter
-    def _branch(self, value: Optional[str]) -> None:
-        state = getattr(self, "_reopen_state", None)
-        if state is not None:
-            state.branch = value
-        else:
-            self._legacy_branch = value
-
-    @property
-    def _checkout_version(self) -> Optional[int]:
-        state = getattr(self, "_reopen_state", None)
-        if state is not None:
-            return state.checkout_version
-        return getattr(self, "_legacy_checkout_version", None)
-
-    @_checkout_version.setter
-    def _checkout_version(self, value: Optional[int]) -> None:
-        state = getattr(self, "_reopen_state", None)
-        if state is not None:
-            state.checkout_version = value
-        else:
-            self._legacy_checkout_version = value
-
-    def _native_state_lock(self):
-        """Return the per-process lock coordinating native mode and reopen state."""
-        pid = os.getpid()
-        guard = getattr(self, "_native_state_guard", None)
-        if guard is None:
-            candidate = (pid, threading.RLock())
-            guard = self.__dict__.setdefault("_native_state_guard", candidate)
-        elif guard[0] != pid:
-            # A lock inherited while another parent thread held it cannot be
-            # safely acquired in the child. Child state starts single-threaded,
-            # so replace it before coordinating the first reopen.
-            guard = (pid, threading.RLock())
-            self._native_state_guard = guard
-        return guard[1]
-
-    @classmethod
-    def _open_from_reopen_state(
-        cls,
-        connection: "DBConnection",
-        state: "_LanceTableReopenState",
-    ) -> "LanceTable":
-        """Open a table from its complete process-independent descriptor."""
-        async_connection = getattr(connection, "_conn", None)
-        if async_connection is None:
-            async_connection = connection._inner
-
-        namespace_client = getattr(connection, "_namespace_client", None)
-        async_table = LOOP.run(
-            async_connection.open_table(
-                state.name,
-                namespace_path=state.namespace_path,
-                storage_options=state.storage_options,
-                index_cache_size=state.index_cache_size,
-                location=state.location,
-                namespace_client=namespace_client,
-                managed_versioning=state.managed_versioning,
-            )
-        )
-        table = cls(
-            connection,
-            state.name,
-            namespace_path=state.namespace_path,
-            storage_options=state.storage_options,
-            index_cache_size=state.index_cache_size,
-            location=state.location,
-            namespace_client=namespace_client,
-            managed_versioning=state.managed_versioning,
-            pushdown_operations=getattr(
-                connection, "_namespace_client_pushdown_operations", None
-            ),
-            route_pushdown_to_rust=getattr(
-                connection, "_route_pushdown_to_rust", False
-            ),
-            _async=async_table,
-        )
-        if state.branch is not None:
-            table = table.branches.checkout(state.branch, state.checkout_version)
-        elif state.checkout_version is not None:
-            table.checkout(state.checkout_version)
-        return table
-
-    def _ensure_open(self) -> None:
-        """Reopen native table handles inherited from another process."""
-        with self._native_state_lock():
-            pid = os.getpid()
-            if getattr(self, "_pid", pid) == pid:
-                return
-
-            state = getattr(self, "_reopen_state", None)
-            fork_reopen_error = getattr(state, "fork_reopen_error", None)
-            if fork_reopen_error is not None:
-                raise RuntimeError(fork_reopen_error)
-            if (
-                state is None
-                or not state.can_reopen_after_fork
-                or state.connection_state is None
-            ):
-                # In-memory and opaque Rust-only connections cannot be recreated
-                # from connection metadata. Their local handles retain the prior
-                # best-effort fork behavior.
-                self._pid = pid
-                return
-
-            from lancedb import deserialize_conn
-
-            connection = deserialize_conn(state.connection_state, for_worker=True)
-            reopened = self._open_from_reopen_state(
-                connection,
-                state,
-            )
-
-            # Keep this Python object stable because user datasets commonly retain
-            # it across fork. Replace every process-bound component with the fresh
-            # child's equivalent.
-            self._conn = reopened._conn
-            self._table = reopened._table
-            self._namespace_client = reopened._namespace_client
-            self._pushdown_operations = reopened._pushdown_operations
-            self._route_pushdown_to_rust = reopened._route_pushdown_to_rust
-            self._reopen_state = reopened._reopen_state
-            self._pid = pid
 
     @property
     def name(self) -> str:
-        if hasattr(self, "_name"):
-            return self._name
-        # Preserve compatibility with lightweight / legacy instances that
-        # were constructed without running ``LanceTable.__init__``.
         return self._table.name
 
     @property
@@ -2530,6 +2446,16 @@ class LanceTable(Table):
     def blob_columns(self) -> list[str]:
         return LOOP.run(self._table.blob_columns())
 
+    def add_bases(
+        self,
+        bases: Union[str, TableBase, Iterable[Union[str, TableBase]]],
+    ) -> None:
+        LOOP.run(self._table.add_bases(bases))
+
+    def list_bases(self) -> list[TableBase]:
+        """Return the additional storage bases for the current table snapshot."""
+        return LOOP.run(self._table.list_bases())
+
     def fetch_blobs(
         self, column: str, row_ids: Union[list[int], pa.Table]
     ) -> pa.LargeBinaryArray:
@@ -2602,75 +2528,18 @@ class LanceTable(Table):
     def _wrap_branch_handle(
         self, async_table: "AsyncTable", version: Optional[int] = None
     ) -> "LanceTable":
-        table = LanceTable(
+        # version is unused locally: the pin already lives on async_table and a
+        # local handle is not reopened via a serialized connection.
+        return LanceTable(
             self._conn,
             async_table.name,
             namespace_path=self._namespace_path,
-            storage_options=self._storage_options,
-            index_cache_size=self._index_cache_size,
             namespace_client=self._namespace_client,
             pushdown_operations=self._pushdown_operations,
             route_pushdown_to_rust=self._route_pushdown_to_rust,
             location=self._location,
-            managed_versioning=self._managed_versioning,
             _async=async_table,
         )
-        table._checkout_version = version
-        return table
-
-    def _resolve_checkout_version(self, version: Union[int, str]) -> int:
-        if isinstance(version, int):
-            return version
-        try:
-            return self.tags.get_version(version)
-        except RuntimeError as err:
-            # Native checkout historically exposes an unknown tag as ValueError.
-            # Preserve that contract while resolving tags before mutating the table.
-            if "Ref not found" in str(err) and "does not exist" in str(err):
-                raise ValueError(str(err)) from err
-            raise
-
-    async def _commit_native_state(
-        self,
-        transition,
-        version: Optional[int],
-        started: threading.Event,
-        finished: threading.Event,
-    ):
-        """Commit a native transition and its fork coordinate as one task."""
-        started.set()
-        try:
-            task = asyncio.ensure_future(transition)
-            try:
-                result = await asyncio.shield(task)
-            except asyncio.CancelledError:
-                # BackgroundEventLoop cancels its submitted task when the
-                # waiting caller is interrupted. Let an already-started native
-                # transition reach its authoritative terminal state before the
-                # per-table boundary is released.
-                result = await task
-                self._checkout_version = version
-                raise
-            self._checkout_version = version
-            return result
-        finally:
-            finished.set()
-
-    def _run_native_state_transition(self, transition, version: Optional[int]):
-        started = threading.Event()
-        finished = threading.Event()
-        try:
-            return LOOP.run(
-                self._commit_native_state(transition, version, started, finished)
-            )
-        except BaseException:
-            if started.is_set():
-                while not finished.is_set():
-                    try:
-                        finished.wait()
-                    except BaseException:  # noqa: PERF203
-                        continue
-            raise
 
     def checkout(self, version: Union[int, str]):
         """Checkout a version of the table. This is an in-place operation.
@@ -2708,14 +2577,7 @@ class LanceTable(Table):
                vector    type
         0  [1.1, 0.9]  vector
         """
-        # Resolve tags before mutating the native handle.  This leaves the live
-        # handle and reopen descriptor aligned if tag lookup fails, and avoids a
-        # second fallible version lookup after checkout succeeds.
-        with self._native_state_lock():
-            resolved_version = self._resolve_checkout_version(version)
-            self._run_native_state_transition(
-                self._table.checkout(resolved_version), resolved_version
-            )
+        LOOP.run(self._table.checkout(version))
 
     def checkout_latest(self):
         """Checkout the latest version of the table. This is an in-place operation.
@@ -2723,8 +2585,7 @@ class LanceTable(Table):
         The table will be set back into standard mode, and will track the latest
         version of the table.
         """
-        with self._native_state_lock():
-            self._run_native_state_transition(self._table.checkout_latest(), None)
+        LOOP.run(self._table.checkout_latest())
 
     def restore(self, version: Optional[Union[int, str]] = None):
         """Restore a version of the table. This is an in-place operation.
@@ -2770,13 +2631,9 @@ class LanceTable(Table):
         >>> len(table.list_versions())
         4
         """
-        with self._native_state_lock():
-            if version is not None:
-                resolved_version = self._resolve_checkout_version(version)
-                self._run_native_state_transition(
-                    self._table.checkout(resolved_version), resolved_version
-                )
-            self._run_native_state_transition(self._table.restore(), None)
+        if version is not None:
+            LOOP.run(self._table.checkout(version))
+        LOOP.run(self._table.restore())
 
     def count_rows(self, filter: Optional[str] = None) -> int:
         return LOOP.run(self._table.count_rows(filter))
@@ -2857,6 +2714,9 @@ class LanceTable(Table):
         2. Currently we've disabled push-down of the filters from polars
            because polars pushdown into pyarrow uses pyarrow compute
            expressions rather than SQl strings (which LanceDB supports)
+        3. The Polars streaming engine is not supported because it does not
+           currently implement Python PyArrow dataset scans. Use the default
+           engine when collecting this LazyFrame.
 
         Returns
         -------
@@ -2865,8 +2725,12 @@ class LanceTable(Table):
         from lancedb.integrations.pyarrow import PyarrowDatasetAdapter
 
         dataset = PyarrowDatasetAdapter(self)
-        return pl.scan_pyarrow_dataset(
-            dataset, allow_pyarrow_filter=False, batch_size=batch_size
+        # Polars 1.32's non-PyArrow callback path passes batch_size twice.  Keep
+        # the compatible PyArrow path, but block predicates because this adapter
+        # cannot translate PyArrow expressions into LanceDB filters.
+        return pl.scan_pyarrow_dataset(dataset, batch_size=batch_size).map_batches(
+            _polars_predicate_pushdown_barrier,
+            predicate_pushdown=False,
         )
 
     # New unified API overload
@@ -3887,9 +3751,7 @@ class LanceTable(Table):
         self = cls.__new__(cls)
         self._conn = db
         self._namespace_path = namespace_path
-        self._index_cache_size = None
         self._location = location
-        self._managed_versioning = None
         self._namespace_client = namespace_client
         self._pushdown_operations = pushdown_operations or set()
         self._route_pushdown_to_rust = route_pushdown_to_rust
@@ -3917,7 +3779,6 @@ class LanceTable(Table):
                 enable_v2_manifest_paths
             )
 
-        self._storage_options = storage_options
         self._table = LOOP.run(
             self._conn._conn.create_table(
                 name,
@@ -3934,7 +3795,6 @@ class LanceTable(Table):
                 namespace_client=namespace_client,
             )
         )
-        self._initialize_reopen_state(name)
         return self
 
     def delete(self, where: Union[str, Expr]) -> DeleteResult:
@@ -4213,9 +4073,28 @@ class LanceTable(Table):
         return LOOP.run(self._table.index_stats(index_name))
 
     def add_columns(
-        self, transforms: Dict[str, str] | pa.field | List[pa.field] | pa.Schema
+        self,
+        transforms: Dict[str, str]
+        | pa.field
+        | List[pa.field]
+        | pa.Schema
+        | None = None,
+        *,
+        computed: Dict[str, str] | None = None,
     ) -> AddColumnsResult:
-        return LOOP.run(self._table.add_columns(transforms))
+        return LOOP.run(self._table.add_columns(transforms, computed=computed))
+
+    def refresh_column(self, column: str) -> "RefreshColumnResult":
+        """Fill a computed column's unfilled rows. See
+        [`AsyncTable.refresh_column`][lancedb.AsyncTable.refresh_column]."""
+        return LOOP.run(self._table.refresh_column(column))
+
+    def refresh_column_async(self, column: str) -> Job:
+        """Fill a computed column's unfilled rows, returning a handle to the
+        refresh job. See
+        [`Table.refresh_column_async`][lancedb.table.Table.refresh_column_async].
+        """
+        return Job(LOOP.run(self._table.refresh_column_async(column)))
 
     def alter_columns(
         self, *alterations: Iterable[Dict[str, str]]
@@ -4250,6 +4129,28 @@ class LanceTable(Table):
         [`AsyncTable.get_lsm_write_spec`][lancedb.AsyncTable.get_lsm_write_spec]."""
         return LOOP.run(self._table.get_lsm_write_spec())
 
+    def checkpoint_lsm(self) -> None:
+        """Synchronous version of
+        [`AsyncTable.checkpoint_lsm`][lancedb.AsyncTable.checkpoint_lsm]."""
+        return LOOP.run(self._table.checkpoint_lsm())
+
+    def flush_lsm(self) -> None:
+        """Synchronous version of
+        [`AsyncTable.flush_lsm`][lancedb.AsyncTable.flush_lsm]."""
+        return LOOP.run(self._table.flush_lsm())
+
+    def compact_lsm(self) -> None:
+        """Synchronous version of
+        [`AsyncTable.compact_lsm`][lancedb.AsyncTable.compact_lsm]."""
+        return LOOP.run(self._table.compact_lsm())
+
+    def get_lsm_stats(self, *, include_generation_rows: bool = False) -> Optional[dict]:
+        """Synchronous version of
+        [`AsyncTable.get_lsm_stats`][lancedb.AsyncTable.get_lsm_stats]."""
+        return LOOP.run(
+            self._table.get_lsm_stats(include_generation_rows=include_generation_rows)
+        )
+
     def close_lsm_writers(self) -> None:
         """Close cached MemWAL shard writers. See
         [`AsyncTable.close_lsm_writers`][lancedb.AsyncTable.close_lsm_writers]."""
@@ -4928,6 +4829,13 @@ class AsyncTable:
         via [`set_unenforced_primary_key`]; bucket sharding additionally
         requires it to be the single column being bucketed.
 
+        By default the MemWAL maintains every index on the table, resolved
+        here — a snapshot, so an index created afterwards needs the spec unset
+        and set again. This fails if one cannot be maintained; name the set
+        with ``with_maintained_indexes`` to install anyway. That pins an exact
+        set (a still-building index is rejected, not omitted); ``[]`` maintains
+        none.
+
         Parameters
         ----------
         spec : LsmWriteSpec
@@ -4954,12 +4862,73 @@ class AsyncTable:
 
         Returns ``None`` when the MemWAL LSM write path is not enabled (no
         spec has been set, or it was removed with `unset_lsm_write_spec`).
-        The returned spec — including its ``maintained_indexes`` and
-        ``writer_config_defaults`` — mirrors what was passed to
-        `set_lsm_write_spec`.
+        The returned spec mirrors what was passed to `set_lsm_write_spec`,
+        except that ``maintained_indexes`` always reports the concrete list
+        resolved when the spec was set — ``None`` never round-trips.
         """
         return await self._inner.get_lsm_write_spec()
 
+    async def checkpoint_lsm(self) -> None:
+        """Converge this table's LSM write path into its base table.
+
+        One flush, sealing every memtable into L0, then compaction triggers
+        until every generation that existed at that moment has reached base.
+        The loop runs client-side, reading progress from ``get_lsm_stats``.
+
+        Best-effort: generations created *while* it runs are deliberately not
+        waited on, which is what lets it terminate on a table taking writes.
+        Idempotent and safe on a cadence.
+
+        There is no deadline, and the caller owns that. It returns when the
+        target generations are gone, raises on a terminal server fault, and
+        otherwise waits however long the server takes. A slow table and a
+        stuck one are the same picture from the client: the compactor pool is
+        shared across every table on the node, so a checkpoint queued behind
+        unrelated work looks exactly like one that is merging. Wrap this in
+        ``asyncio.wait_for`` for a wall-clock bound; abandoning it partway
+        costs nothing.
+        """
+        return await self._inner.checkpoint_lsm()
+
+    async def flush_lsm(self) -> None:
+        """Seal every bucket's active memtable into L0.
+
+        Does not touch the base table — moving L0 into base is
+        `compact_lsm`. On a node that has not claimed this table, this claims
+        it and replays its WAL log first.
+        """
+        return await self._inner.flush_lsm()
+
+    async def compact_lsm(self) -> None:
+        """Trigger a background L0 to base compaction pass per bucket.
+
+        Returns once the passes are dispatched, not once they finish: watch
+        ``get_lsm_stats`` for progress, or use ``checkpoint_lsm`` to loop
+        until the current L0 has reached base.
+        """
+        return await self._inner.compact_lsm()
+
+    async def get_lsm_stats(
+        self, *, include_generation_rows: bool = False
+    ) -> Optional[dict]:
+        """Read live per-bucket LSM state.
+
+        Answers "how far behind is my fresh tier", "which bucket is hot", and
+        "why is my fresh-tier vector search brute-force". Mutates no table
+        state, though on a node that has not claimed this table it claims it,
+        exactly as a read would.
+
+        Returns ``None`` only when the LSM write path is not enabled.
+
+        Parameters
+        ----------
+        include_generation_rows
+            Report a row count per L0 generation. Off by default: each count
+            opens an uncached Lance dataset, and ``checkpoint_lsm`` polls this
+            needing only generation numbers.
+        """
+        return await self._inner.get_lsm_stats(include_generation_rows)
+
     async def close_lsm_writers(self) -> None:
         """Drain and close any cached MemWAL shard writers for this table.
 
@@ -6040,7 +6009,14 @@ class AsyncTable:
         return await self._inner.update(updates_sql, where)
 
     async def add_columns(
-        self, transforms: dict[str, str] | pa.field | List[pa.field] | pa.Schema
+        self,
+        transforms: dict[str, str]
+        | pa.field
+        | List[pa.field]
+        | pa.Schema
+        | None = None,
+        *,
+        computed: dict[str, str] | None = None,
     ) -> AddColumnsResult:
         """
         Add new columns with defined values.
@@ -6053,6 +6029,22 @@ class AsyncTable:
             each row in the table, and can reference existing columns.
             Alternatively, you can pass a pyarrow field or schema to add
             new columns with NULLs.
+        computed: Dict[str, str], optional
+            A map of column name to a SQL expression defining the column. The
+            column's type and inputs are derived from the expression.
+
+            Unlike ``transforms``, the expression is stored rather than
+            evaluated now: the column is committed with no values, and rows get
+            them from
+            [`refresh_column`][lancedb.table.AsyncTable.refresh_column].
+
+            A refresh does not revisit rows it has already filled, so mutating
+            an input leaves the value computed at fill time. While a
+            declaration reads a column, that column cannot be renamed, retyped
+            or dropped.
+
+            On LanceDB Cloud and Enterprise the expression is planned by
+            the server. Cannot be combined with ``transforms``.
 
         Returns
         -------
@@ -6066,11 +6058,71 @@ class AsyncTable:
             {isinstance(f, pa.Field) for f in transforms}
         ):
             transforms = pa.schema(transforms)
+        if computed:
+            if transforms:
+                raise ValueError(
+                    "add_columns cannot take both transforms and computed columns"
+                )
+            return await self._inner.add_computed_columns(list(computed.items()))
+        if transforms is None:
+            raise ValueError("add_columns requires transforms or computed columns")
         if isinstance(transforms, pa.Schema):
             return await self._inner.add_columns_with_schema(transforms)
         else:
             return await self._inner.add_columns(list(transforms.items()))
 
+    async def refresh_column(self, column: str) -> RefreshColumnResult:
+        """
+        Fill the rows of a computed column that hold no value yet.
+
+        Declared with ``add_columns(computed=...)``, a column starts empty and
+        gets its values here. Rows appended since the last refresh are filled
+        by the next one; rows already filled are left as they are, so the call
+        is idempotent and does not observe a mutated input.
+
+        Local tables only: a remote refresh runs as a server job, through
+        [`refresh_column_async`][lancedb.table.Table.refresh_column_async].
+
+        Parameters
+        ----------
+        column: str
+            The name of the computed column to fill.
+
+        Returns
+        -------
+        RefreshColumnResult
+            The number of rows filled and the new version of the table.
+        """
+        return await self._inner.refresh_column(column)
+
+    async def refresh_column_async(self, column: str) -> AsyncJob:
+        """
+        Like :meth:`refresh_column`, but returns a handle to the refresh job
+        instead of blocking until it completes.
+
+        The job may already be complete when returned; callers must not assume
+        the column is filled until :meth:`AsyncJob.wait` resolves. Invalid
+        input -- an unknown column, or one that is not computed -- raises here
+        rather than failing the job. On local tables the job runs
+        in-process; on LanceDB Cloud and Enterprise it is the server's
+        backfill job.
+
+        Examples
+        --------
+        >>> import asyncio
+        >>> import lancedb
+        >>> async def refresh_in_background():
+        ...     db = await lancedb.connect_async("./.lancedb")
+        ...     table = await db.create_table("computed_job_async_demo", [{"x": 1}])
+        ...     await table.add_columns(computed={"doubled": "x * 2"})
+        ...     job = await table.refresh_column_async("doubled")
+        ...     await job.wait()
+        ...     return await job.status()
+        >>> asyncio.run(refresh_in_background())
+        'finished'
+        """
+        return AsyncJob(await self._inner.refresh_column_async(column))
+
     async def alter_columns(
         self, *alterations: Iterable[dict[str, Any]]
     ) -> AlterColumnsResult:
@@ -6256,6 +6308,25 @@ class AsyncTable:
     async def blob_columns(self) -> list[str]:
         return await self._inner.blob_columns()
 
+    async def add_bases(
+        self,
+        bases: Union[str, TableBase, Iterable[Union[str, TableBase]]],
+    ) -> None:
+        """Register additional storage bases for this table.
+
+        A URI string is a non-root base with no alias::
+
+            await table.add_bases("s3://bucket/media/")
+        """
+        await self._inner.add_bases(_normalize_bases(bases))
+
+    async def list_bases(self) -> list[TableBase]:
+        """Return the additional storage bases for the current table snapshot."""
+        return [
+            TableBase(path=path, name=name, is_dataset_root=is_dataset_root)
+            for path, name, is_dataset_root in await self._inner.list_bases()
+        ]
+
     async def fetch_blobs(
         self, column: str, row_ids: Union[list[int], pa.Table]
     ) -> pa.LargeBinaryArray:
@@ -6474,6 +6545,30 @@ class AsyncTable:
         await self._inner.replace_field_metadata(field_name, new_metadata)
 
 
+def _normalize_bases(
+    base_inputs: Union[str, TableBase, Iterable[Union[str, TableBase]]],
+) -> list[TableBase]:
+    if isinstance(base_inputs, (str, TableBase)):
+        items: Iterable[Union[str, TableBase]] = [base_inputs]
+    elif isinstance(base_inputs, Mapping):
+        raise TypeError(
+            "Expected a URI string, TableBase, or an iterable of those values"
+        )
+    else:
+        items = base_inputs
+    normalized_bases: list[TableBase] = []
+    for base in items:
+        if isinstance(base, str):
+            normalized_bases.append(TableBase(path=base))
+        elif isinstance(base, TableBase):
+            normalized_bases.append(base)
+        else:
+            raise TypeError(
+                f"Expected a URI string or TableBase, got {type(base).__name__}"
+            )
+    return normalized_bases
+
+
 @dataclass
 class IndexStatistics:
     """
@@ -6525,7 +6620,9 @@ class TableStatistics:
     Attributes
     ----------
     total_bytes: int
-        The total number of bytes in the table.
+        The total size, in bytes, of the table's data files, index files, and
+        overlay files. Read from the manifest, so this excludes deletion files
+        and manifests.
     num_rows: int
         The total number of rows in the table.
     num_indices: int

python/python/tests/test_bases.py

@@ -0,0 +1,97 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright The LanceDB Authors
+
+import pyarrow as pa
+import pytest
+
+import lancedb
+
+
+def test_list_bases_reflects_added_bases(tmp_path):
+    media = tmp_path / "media"
+    media.mkdir()
+    db = lancedb.connect(tmp_path / "db")
+    schema = pa.schema([pa.field("id", pa.int64())])
+    table = db.create_table("photos", schema=schema)
+    assert table.list_bases() == []
+    table.add_bases(media.as_uri())
+    assert table.list_bases() == [lancedb.TableBase(path=media.as_uri())]
+
+
+def test_add_bases_accepts_two_unnamed_paths(tmp_path):
+    media = tmp_path / "media"
+    other = tmp_path / "other"
+    media.mkdir()
+    other.mkdir()
+    db = lancedb.connect(tmp_path / "db")
+    schema = pa.schema([pa.field("id", pa.int64())])
+    table = db.create_table("photos", schema=schema)
+    table.add_bases([media.as_uri(), other.as_uri()])
+    assert table.list_bases() == [
+        lancedb.TableBase(path=media.as_uri()),
+        lancedb.TableBase(path=other.as_uri()),
+    ]
+
+
+def test_add_bases_records_name_and_dataset_root(tmp_path):
+    media = tmp_path / "media"
+    parent = tmp_path / "parent"
+    media.mkdir()
+    parent.mkdir()
+    db = lancedb.connect(tmp_path / "db")
+    schema = pa.schema([pa.field("id", pa.int64())])
+    table = db.create_table("photos", schema=schema)
+    table.add_bases(
+        [
+            lancedb.TableBase(path=media.as_uri(), name="media", is_dataset_root=False),
+            lancedb.TableBase(
+                path=parent.as_uri(), name="parent", is_dataset_root=True
+            ),
+        ]
+    )
+    assert table.list_bases() == [
+        lancedb.TableBase(path=media.as_uri(), name="media", is_dataset_root=False),
+        lancedb.TableBase(path=parent.as_uri(), name="parent", is_dataset_root=True),
+    ]
+
+
+def test_add_bases_rejects_dict_input(tmp_path):
+    db = lancedb.connect(tmp_path / "db")
+    schema = pa.schema([pa.field("id", pa.int64())])
+    table = db.create_table("photos", schema=schema)
+    with pytest.raises(TypeError, match="TableBase"):
+        table.add_bases({"path": "s3://bucket/media/"})
+
+
+@pytest.mark.asyncio
+async def test_async_add_bases_accepts_file_uri(tmp_path):
+    media = tmp_path / "media"
+    media.mkdir()
+    db = await lancedb.connect_async(tmp_path / "db")
+    schema = pa.schema([pa.field("id", pa.int64())])
+    table = await db.create_table("photos", schema=schema)
+    assert await table.list_bases() == []
+    await table.add_bases(media.as_uri())
+    assert await table.list_bases() == [lancedb.TableBase(path=media.as_uri())]
+
+
+def test_memory_add_bases_accepts_file_uri(tmp_path):
+    media = tmp_path / "media"
+    media.mkdir()
+    db = lancedb.connect("memory:///")
+    schema = pa.schema([pa.field("id", pa.int64())])
+    table = db.create_table("photos", schema=schema)
+    assert table.list_bases() == []
+    table.add_bases(media.as_uri())
+    assert table.list_bases() == [lancedb.TableBase(path=media.as_uri())]
+
+
+def test_namespace_add_bases_accepts_file_uri(tmp_path):
+    media = tmp_path / "media"
+    media.mkdir()
+    db = lancedb.connect_namespace("dir", {"root": str(tmp_path / "ns")})
+    schema = pa.schema([pa.field("id", pa.int64())])
+    table = db.create_table("photos", schema=schema)
+    assert table.list_bases() == []
+    table.add_bases(media.as_uri())
+    assert table.list_bases() == [lancedb.TableBase(path=media.as_uri())]

python/python/tests/test_db.py

@@ -2,11 +2,11 @@
 # SPDX-FileCopyrightText: Copyright The LanceDB Authors
 
 
-import json
 import inspect
 import re
 import sys
 from datetime import timedelta
+from importlib import resources
 import os
 from types import SimpleNamespace
 
@@ -19,6 +19,10 @@ from lance_namespace.errors import NamespaceNotEmptyError, TableNotFoundError
 from lancedb.pydantic import LanceModel, Vector
 
 
+def test_package_includes_pep_561_marker():
+    assert resources.files(lancedb).joinpath("py.typed").is_file()
+
+
 def test_basic(tmp_path):
     db = lancedb.connect(tmp_path)
 
@@ -102,17 +106,6 @@ def test_read_consistency_interval_does_not_use_background_loop(tmp_path, monkey
     assert db_from_inner.read_consistency_interval == consistency_interval
 
 
-def test_serialize_preserves_zero_read_consistency_interval(tmp_path):
-    db = lancedb.connect(tmp_path, read_consistency_interval=timedelta(0))
-    table = db.create_table("items", pa.table({"x": [1]}))
-
-    encoded = json.loads(table._connection_state)
-    assert encoded["read_consistency_interval_seconds"] == 0.0
-
-    restored = lancedb.deserialize_conn(table._connection_state)
-    assert restored.read_consistency_interval == timedelta(0)
-
-
 def test_ingest_pd(tmp_path):
     db = lancedb.connect(tmp_path)
 
@@ -762,8 +755,7 @@ def test_delete_table(tmp_db: lancedb.DBConnection):
     assert tmp_db.table_names() == []
 
 
-@pytest.mark.asyncio
-async def test_delete_table_async(tmp_db: lancedb.DBConnection):
+def test_drop_table_async(tmp_db: lancedb.DBConnection):
     data = pd.DataFrame(
         {
             "vector": [[3.1, 4.1], [5.9, 26.5]],
@@ -779,7 +771,10 @@ async def test_delete_table_async(tmp_db: lancedb.DBConnection):
 
     assert tmp_db.table_names() == ["test"]
 
-    tmp_db.drop_table("test")
+    job = tmp_db.drop_table_async("test")
+    assert job.id is None
+    assert job.status() == "finished"
+    job.wait()
     assert tmp_db.table_names() == []
 
     tmp_db.create_table("test", data=data)
@@ -788,6 +783,17 @@ async def test_delete_table_async(tmp_db: lancedb.DBConnection):
     tmp_db.drop_table("does_not_exist", ignore_missing=True)
 
 
+@pytest.mark.asyncio
+async def test_drop_table_async_connection(tmp_db_async: lancedb.AsyncConnection):
+    await tmp_db_async.create_table("test", data=pa.table({"id": [1, 2]}))
+
+    job = await tmp_db_async.drop_table_async("test")
+    assert job.id is None
+    assert await job.status() == "finished"
+    await job.wait()
+    assert await tmp_db_async.table_names() == []
+
+
 def test_drop_database(tmp_db: lancedb.DBConnection):
     data = pd.DataFrame(
         {

python/python/tests/test_elastic_dataloader.py

@@ -1456,6 +1456,408 @@ def test_shuffle_clump_size_yields_all_rows(lance_table):
     )
 
 
+# ---------------------------------------------------------------------------
+# on_transform_error tests
+# ---------------------------------------------------------------------------
+
+
+class BadRowError(ValueError):
+    """Raised by the failing transforms below when a batch contains a bad id."""
+
+
+def _failing_transform(bad_ids: set):
+    """A transform that raises BadRowError whenever the batch has a bad id.
+
+    Raises on the full batch and on any single-row slice containing a bad id,
+    so per-row isolation drops exactly the bad rows.
+    """
+
+    def transform(batch: pa.RecordBatch) -> list:
+        ids = batch.column("id").to_pylist()
+        bad = sorted(set(ids) & bad_ids)
+        if bad:
+            raise BadRowError(f"bad ids in batch: {bad}")
+        return [{"id": i} for i in ids]
+
+    return transform
+
+
+def _sequential_split_members(table) -> list[list[int]]:
+    """Return each split's ids in yield order for shuffle=False.
+
+    With a single rank and no workers the round-robin yields one row per split
+    per cycle, so item k of a clean run belongs to split k % NUM_SPLITS.
+    """
+    ds = StreamingDataset(table, num_splits=NUM_SPLITS, shuffle=False)
+    members: list[list[int]] = [[] for _ in range(NUM_SPLITS)]
+    for k, row in enumerate(ds):
+        members[k % NUM_SPLITS].append(row["id"])
+    return members
+
+
+def test_on_transform_error_default_raises(lance_table):
+    """By default a transform exception propagates and aborts iteration."""
+    ds = StreamingDataset(
+        lance_table,
+        num_splits=NUM_SPLITS,
+        shuffle_seed=SHUFFLE_SEED,
+        transform=_failing_transform({7}),
+    )
+    with pytest.raises(BadRowError):
+        list(ds)
+
+
+def test_on_transform_error_invalid_value(lance_table):
+    with pytest.raises(ValueError, match="on_transform_error"):
+        StreamingDataset(lance_table, num_splits=NUM_SPLITS, on_transform_error="bogus")
+
+
+def test_on_transform_error_skip_drops_bad_rows(lance_table):
+    """With one bad row per split, 'skip' yields every good row exactly once
+    and counts the dropped rows in rows_skipped."""
+    members = _sequential_split_members(lance_table)
+    bad_ids = {members[i][4] for i in range(NUM_SPLITS)}
+
+    ds = StreamingDataset(
+        lance_table,
+        num_splits=NUM_SPLITS,
+        shuffle=False,
+        transform=_failing_transform(bad_ids),
+        on_transform_error="skip",
+    )
+    assert ds.rows_skipped == 0
+
+    ids = [row["id"] for row in ds]
+
+    assert sorted(ids) == sorted(set(range(NUM_ROWS)) - bad_ids)
+    assert ds.rows_skipped == NUM_SPLITS
+
+
+def test_on_transform_error_skip_uneven_ends_at_last_complete_cycle(lance_table):
+    """When one split loses more rows than the others, the epoch ends at the
+    last cycle where every split still has a row — no crash, no bad rows, and
+    every step remains one sample per split."""
+    members = _sequential_split_members(lance_table)
+    bad_ids = set(members[0][:3])  # all 3 bad rows in split 0
+
+    ds = StreamingDataset(
+        lance_table,
+        num_splits=NUM_SPLITS,
+        shuffle=False,
+        transform=_failing_transform(bad_ids),
+        on_transform_error="skip",
+    )
+    items = [row["id"] for row in ds]
+
+    rows_per_split = NUM_ROWS // NUM_SPLITS
+    expected_cycles = rows_per_split - len(bad_ids)
+    assert len(items) == expected_cycles * NUM_SPLITS
+    assert len(set(items)) == len(items), "duplicate samples yielded"
+    assert not set(items) & bad_ids, "a bad row was yielded"
+    # Split 0 contributed exactly its surviving rows, in order, one per cycle.
+    survivors = [i for i in members[0] if i not in bad_ids]
+    assert items[0::NUM_SPLITS] == survivors[:expected_cycles]
+
+
+def test_on_transform_error_warn_logs(lance_table, caplog):
+    """'warn' skips like 'skip' but logs a warning for the failing batch."""
+    members = _sequential_split_members(lance_table)
+    bad_ids = {members[i][3] for i in range(NUM_SPLITS)}
+
+    ds = StreamingDataset(
+        lance_table,
+        num_splits=NUM_SPLITS,
+        shuffle=False,
+        transform=_failing_transform(bad_ids),
+        on_transform_error="warn",
+    )
+    with caplog.at_level(logging.WARNING, logger="lancedb.streaming"):
+        items = list(ds)
+
+    assert len(items) == NUM_ROWS - NUM_SPLITS
+    assert ds.rows_skipped == NUM_SPLITS
+    assert "Skipped" in caplog.text
+    assert "BadRowError" in caplog.text
+
+
+def test_on_transform_error_callable_selective(lance_table):
+    """A callable handler can skip expected errors and re-raise the rest."""
+    members = _sequential_split_members(lance_table)
+    bad_ids = {members[i][0] for i in range(NUM_SPLITS)}
+
+    handled: list[Exception] = []
+
+    def handler(exc: Exception) -> bool:
+        handled.append(exc)
+        return isinstance(exc, BadRowError)
+
+    ds = StreamingDataset(
+        lance_table,
+        num_splits=NUM_SPLITS,
+        shuffle=False,
+        transform=_failing_transform(bad_ids),
+        on_transform_error=handler,
+    )
+    items = list(ds)
+    assert len(items) == NUM_ROWS - NUM_SPLITS
+    assert handled and all(isinstance(exc, BadRowError) for exc in handled)
+
+    def broken_transform(batch: pa.RecordBatch) -> list:
+        raise TypeError("boom")
+
+    ds2 = StreamingDataset(
+        lance_table,
+        num_splits=NUM_SPLITS,
+        shuffle=False,
+        transform=broken_transform,
+        on_transform_error=handler,
+    )
+    with pytest.raises(TypeError, match="boom"):
+        list(ds2)
+
+
+def test_transform_wrong_row_count_raises(lance_table):
+    """A transform that returns the wrong number of rows is an error even with
+    on_transform_error='skip' — silent shrinkage would corrupt accounting."""
+
+    def drops_rows(batch: pa.RecordBatch) -> list:
+        return batch.column("id").to_pylist()[:-1]
+
+    ds = StreamingDataset(
+        lance_table,
+        num_splits=NUM_SPLITS,
+        shuffle_seed=SHUFFLE_SEED,
+        transform=drops_rows,
+        on_transform_error="skip",
+    )
+    with pytest.raises(ValueError, match="one output row per input row"):
+        list(ds)
+
+
+def test_skip_deterministic_across_runs(lance_table):
+    """With a fixed seed, skipping produces the identical sample sequence on
+    every run — skips are data-dependent, not run-dependent."""
+    bad_ids = {5, 17, 46}
+
+    def run() -> tuple[list[int], int]:
+        ds = StreamingDataset(
+            lance_table,
+            num_splits=NUM_SPLITS,
+            shuffle_seed=SHUFFLE_SEED,
+            transform=_failing_transform(bad_ids),
+            on_transform_error="skip",
+        )
+        return [row["id"] for row in ds], ds.rows_skipped
+
+    ids_a, skipped_a = run()
+    ids_b, skipped_b = run()
+    assert ids_a == ids_b
+    assert skipped_a == skipped_b
+    assert not set(ids_a) & bad_ids
+
+
+def test_skip_elastic_det_across_world_sizes(lance_table):
+    """With equal bad-row counts per split, skipping preserves the full
+    elastic-determinism guarantee: identical global batches at every step for
+    every compatible world_size."""
+    members = _sequential_split_members(lance_table)
+    bad_ids = {members[i][6] for i in range(NUM_SPLITS)}
+
+    def collect(world_size: int) -> list[frozenset[int]]:
+        micro = GLOBAL_BATCH_SIZE // world_size
+        iters = [
+            iter(
+                StreamingDataset(
+                    lance_table,
+                    num_splits=NUM_SPLITS,
+                    shuffle=False,
+                    rank=rank,
+                    world_size=world_size,
+                    transform=_failing_transform(bad_ids),
+                    on_transform_error="skip",
+                )
+            )
+            for rank in range(world_size)
+        ]
+        _STOP = object()
+        batches: list[frozenset[int]] = []
+        while True:
+            step_samples: set[int] = set()
+            exhausted = 0
+            for it in iters:
+                for _ in range(micro):
+                    val = next(it, _STOP)
+                    if val is _STOP:
+                        exhausted += 1
+                        break
+                    step_samples.add(val["id"])
+            if exhausted == len(iters):
+                break
+            assert exhausted == 0, (
+                "Rank iterators exhausted at different steps despite equal "
+                "bad-row counts per split"
+            )
+            batches.append(frozenset(step_samples))
+        return batches
+
+    reference = collect(1)
+    assert len(reference) == NUM_ROWS // NUM_SPLITS - 1
+    for ws in (2, 3, 4):
+        assert collect(ws) == reference, f"world_size={ws} diverged"
+
+
+def test_resumability_with_skips_same_topology(lance_table):
+    """Checkpointing mid-epoch with skipped rows resumes exactly: no sample
+    repeated, no sample lost, skipped rows stay skipped."""
+    members = _sequential_split_members(lance_table)
+    # Uneven skips: positions diverge across splits (2 bad in split 0, 1 in
+    # split 5), which only a position-based checkpoint can resume exactly.
+    bad_ids = {members[0][2], members[0][3], members[5][7]}
+    kwargs = dict(
+        num_splits=NUM_SPLITS,
+        shuffle=False,
+        transform=_failing_transform(bad_ids),
+        on_transform_error="skip",
+    )
+
+    reference = [row["id"] for row in StreamingDataset(lance_table, **kwargs)]
+    rows_per_split = NUM_ROWS // NUM_SPLITS
+    assert len(reference) == (rows_per_split - 2) * NUM_SPLITS
+
+    steps = 3
+    ds = StreamingDataset(lance_table, **kwargs)
+    it = iter(ds)
+    consumed = [next(it)["id"] for _ in range(steps * NUM_SPLITS)]
+    checkpoint = ds.state_dict()
+    it.close()
+
+    # Split 0 skipped positions 2 and 3 within its first 3 yields; split 5's
+    # bad row is beyond the checkpoint.  Everything else is at 3 = the sample
+    # count.
+    positions = checkpoint["positions_consumed_per_split"]
+    assert positions[0] == 5
+    assert positions[1:] == [3] * (NUM_SPLITS - 1)
+    assert checkpoint["samples_consumed_per_split"] == [3] * NUM_SPLITS
+
+    ds2 = StreamingDataset(lance_table, **kwargs)
+    ds2.load_state_dict(checkpoint)
+    resumed = [row["id"] for row in ds2]
+
+    assert consumed == reference[: steps * NUM_SPLITS]
+    assert resumed == reference[steps * NUM_SPLITS :]
+
+
+def test_resumability_with_skips_elastic_merge(lance_table):
+    """Elastic resume with skips: each rank's checkpoint knows exact positions
+    only for its own splits; merge_state_dicts recovers the global state, and
+    a run on a different world_size continues exactly."""
+    members = _sequential_split_members(lance_table)
+    # Bad rows early in split 0 (rank 0) and split 6 (rank 1 of a ws=2 run) so
+    # both ranks' position vectors diverge before the checkpoint.
+    bad_ids = {members[0][0], members[0][2], members[6][1]}
+    kwargs = dict(
+        num_splits=NUM_SPLITS,
+        shuffle=False,
+        transform=_failing_transform(bad_ids),
+        on_transform_error="skip",
+    )
+
+    reference = [row["id"] for row in StreamingDataset(lance_table, **kwargs)]
+
+    steps = 3
+    world_size = 2
+    micro = GLOBAL_BATCH_SIZE // world_size
+    datasets = [
+        StreamingDataset(lance_table, rank=rank, world_size=world_size, **kwargs)
+        for rank in range(world_size)
+    ]
+    iters = [iter(ds) for ds in datasets]
+    seen: list[frozenset[int]] = []
+    for _ in range(steps):
+        step_samples = set()
+        for it in iters:
+            for _ in range(micro):
+                step_samples.add(next(it)["id"])
+        seen.append(frozenset(step_samples))
+    states = [ds.state_dict() for ds in datasets]
+    for it in iters:
+        it.close()
+
+    merged = StreamingDataset.merge_state_dicts(states)
+    expected_positions = [3] * NUM_SPLITS
+    expected_positions[0] = 5  # skipped positions 0 and 2
+    expected_positions[6] = 4  # skipped position 1
+    assert merged["positions_consumed_per_split"] == expected_positions
+
+    # The first 3 global batches match the world_size=1 reference.
+    ref_batches = [
+        frozenset(reference[s * NUM_SPLITS : (s + 1) * NUM_SPLITS])
+        for s in range(len(reference) // NUM_SPLITS)
+    ]
+    assert seen == ref_batches[:steps]
+
+    # Resume on world_size=1 from the merged state.
+    ds_resume = StreamingDataset(lance_table, **kwargs)
+    ds_resume.load_state_dict(merged)
+    resumed = [row["id"] for row in ds_resume]
+    assert resumed == reference[steps * NUM_SPLITS :]
+
+
+def test_rows_skipped_flushed_when_split_entirely_bad(lance_table):
+    """A split whose rows all fail never completes a cycle, so the epoch ends
+    immediately — but rows_skipped must still report the drops after the
+    iterator exits (the shared-memory counter is flushed on exhaustion)."""
+    members = _sequential_split_members(lance_table)
+    bad_ids = set(members[0])  # every row of split 0 is bad
+
+    ds = StreamingDataset(
+        lance_table,
+        num_splits=NUM_SPLITS,
+        shuffle=False,
+        transform=_failing_transform(bad_ids),
+        on_transform_error="skip",
+    )
+    assert list(ds) == []
+    assert ds.rows_skipped == len(bad_ids)
+
+
+def test_merge_state_dicts_validates_consistency(lance_table):
+    ds = StreamingDataset(lance_table, num_splits=NUM_SPLITS, shuffle_seed=SHUFFLE_SEED)
+    state = ds.state_dict()
+    other = dict(state, shuffle_seed=SHUFFLE_SEED + 1)
+    with pytest.raises(ValueError, match="shuffle_seed mismatch"):
+        StreamingDataset.merge_state_dicts([state, other])
+    with pytest.raises(ValueError, match="at least one"):
+        StreamingDataset.merge_state_dicts([])
+
+
+def test_load_state_dict_without_positions_key(lance_table):
+    """Checkpoints from before positions_consumed_per_split existed still
+    resume exactly (positions equal sample counts when nothing is skipped)."""
+    reference = [
+        row["id"]
+        for row in StreamingDataset(
+            lance_table, num_splits=NUM_SPLITS, shuffle_seed=SHUFFLE_SEED
+        )
+    ]
+
+    steps = 4
+    ds = StreamingDataset(lance_table, num_splits=NUM_SPLITS, shuffle_seed=SHUFFLE_SEED)
+    it = iter(ds)
+    for _ in range(steps * NUM_SPLITS):
+        next(it)
+    checkpoint = ds.state_dict()
+    it.close()
+    del checkpoint["positions_consumed_per_split"]
+
+    ds2 = StreamingDataset(
+        lance_table, num_splits=NUM_SPLITS, shuffle_seed=SHUFFLE_SEED
+    )
+    ds2.load_state_dict(checkpoint)
+    resumed = [row["id"] for row in ds2]
+    assert resumed == reference[steps * NUM_SPLITS :]
+
+
 def test_num_splits_defaults_to_world_size(lance_table):
     """Omitting num_splits gives world_size splits (one per rank)."""
     ds = StreamingDataset(

python/python/tests/test_embeddings.py

@@ -631,3 +631,23 @@ def test_url_retrieve_downloads_image():
     image_bytes = url_retrieve(image_url)
     img = Image.open(io.BytesIO(image_bytes))
     assert img.size[0] > 0 and img.size[1] > 0
+
+
+def test_jina_generate_image_input_dict_local_path(tmp_path):
+    """
+    JinaEmbeddings._generate_image_input_dict must accept a local image path
+    (str or Path), not just bytes. Previously it crashed with
+    `AttributeError: 'function' object has no attribute 'urlparse'` on any
+    str/Path input because it called `urlparse.urlparse(image)` instead of
+    `urlparse(image)` (urlparse was imported as a function, not a module).
+    """
+    Image = pytest.importorskip("PIL.Image")
+    from lancedb.embeddings.jinaai import JinaEmbeddings
+
+    image_path = tmp_path / "test.png"
+    Image.new("RGB", (4, 4), color="red").save(image_path, format="PNG")
+
+    for image in (str(image_path), image_path):
+        image_dict = JinaEmbeddings._generate_image_input_dict(image)
+        assert "image" in image_dict
+        assert isinstance(image_dict["image"], str) and len(image_dict["image"]) > 0

python/python/tests/test_lsm_write_spec.py

@@ -83,7 +83,9 @@ def test_lsm_write_spec_repr():
     assert s.spec_type == "bucket"
     assert s.column == "id"
     assert s.num_buckets == 4
-    assert s.maintained_indexes == []
+    # A fresh spec defers its maintained set to install time.
+    assert s.maintained_indexes is None
+    assert s.with_maintained_indexes([]).maintained_indexes == []
     assert "bucket" in repr(s)
     assert "id" in repr(s)
     assert "4" in repr(s)
@@ -169,18 +171,23 @@ def test_get_lsm_write_spec(tmp_path):
     table.unset_lsm_write_spec()
     assert table.get_lsm_write_spec() is None
 
-    # Identity round-trips (column recovered from the schema).
+    # Identity round-trips (column recovered from the schema). Leaving the
+    # maintained set to be inferred picks up the index on the table, so the
+    # spec reads back naming it rather than as "infer".
     table.set_lsm_write_spec(LsmWriteSpec.identity("id"))
     spec = table.get_lsm_write_spec()
     assert spec.spec_type == "identity"
     assert spec.column == "id"
+    assert spec.maintained_indexes == [idx_name]
     table.unset_lsm_write_spec()
 
-    # Unsharded round-trips (no routing column).
-    table.set_lsm_write_spec(LsmWriteSpec.unsharded())
+    # Unsharded round-trips (no routing column). Opting out is distinct from
+    # the inferred default.
+    table.set_lsm_write_spec(LsmWriteSpec.unsharded().with_maintained_indexes([]))
     spec = table.get_lsm_write_spec()
     assert spec.spec_type == "unsharded"
     assert spec.column is None
+    assert spec.maintained_indexes == []
 
 
 @pytest.mark.asyncio

python/python/tests/test_merge_insert_lsm.py

@@ -544,7 +544,7 @@ def test_lsm_read_fts_unmaintained_index_errors(tmp_path):
     table.create_index("text", config=FTS())
     # No maintained indexes: the active memtable FTS arm cannot serve un-compacted
     # docs, so the search would silently omit them — reject instead.
-    table.set_lsm_write_spec(LsmWriteSpec.unsharded())
+    table.set_lsm_write_spec(LsmWriteSpec.unsharded().with_maintained_indexes([]))
     with pytest.raises(Exception, match="maintained"):
         table.search("fox", query_type="fts", fts_columns="text").to_arrow()
 
@@ -631,7 +631,7 @@ def test_lsm_read_vector_unmaintained_index_errors(tmp_path):
     )
     # Spec with NO maintained indexes: the base vector index's catch-up is untracked,
     # so the scanner rejects rather than risk dropping compacted-but-unindexed rows.
-    table.set_lsm_write_spec(LsmWriteSpec.unsharded())
+    table.set_lsm_write_spec(LsmWriteSpec.unsharded().with_maintained_indexes([]))
     with pytest.raises(Exception, match="maintained"):
         table.search([1.0] * VECTOR_DIM).to_arrow()
 

python/python/tests/test_namespace.py

@@ -6,13 +6,9 @@
 import tempfile
 import shutil
 import importlib
-import multiprocessing as mp
-import sys
-from datetime import timedelta
 import pytest
 import pyarrow as pa
 import lancedb
-from lance_namespace import connect as namespace_connect
 from lance_namespace.errors import NamespaceNotEmptyError, TableNotFoundError
 from lancedb.namespace import _MAX_QUERY_K
 from lancedb.table import AsyncTable, LanceTable
@@ -76,16 +72,6 @@ def _namespace_lance_table(namespace_client: _NamespaceClient) -> LanceTable:
     return table
 
 
-def _direct_namespace_fork_child(table, result_queue):
-    from lancedb.permutation import Permutation
-
-    try:
-        permutation = Permutation.identity(table)
-        result_queue.put(("ok", permutation.num_rows))
-    except Exception as error:
-        result_queue.put((type(error).__name__, str(error)))
-
-
 class TestNamespaceConnection:
     """Test namespace-based LanceDB connection using DirectoryNamespace."""
 
@@ -433,95 +419,7 @@ class TestNamespaceConnection:
                 pa.field("vector", pa.list_(pa.float32(), 2)),
             ]
         )
-        created = db.create_table(
-            "test_table", schema=schema, storage_options=table_opts
-        )
-        assert created._storage_options == table_opts
-
-        opened = db.open_table(
-            "test_table",
-            storage_options={"allow_http": "true"},
-            index_cache_size=17,
-        )
-        assert opened._storage_options == {"allow_http": "true"}
-        assert opened._index_cache_size == 17
-        opened._pid = -1
-        opened._ensure_open()
-        assert opened.count_rows() == 0
-
-    def test_serialize_preserves_zero_read_consistency_interval(self):
-        db = lancedb.connect_namespace(
-            "dir",
-            {"root": self.temp_dir},
-            read_consistency_interval=timedelta(0),
-        )
-
-        restored = lancedb.deserialize_conn(db.serialize())
-        assert restored.read_consistency_interval == timedelta(0)
-
-    @pytest.mark.skipif(
-        sys.platform != "linux",
-        reason="fork() is only supported safely for this test on Linux",
-    )
-    def test_direct_namespace_with_descriptor_reopens_after_fork(self):
-        properties = {"root": self.temp_dir}
-        namespace = namespace_connect("dir", properties)
-        db = lancedb.LanceNamespaceDBConnection(
-            namespace,
-            namespace_client_impl="dir",
-            namespace_client_properties=properties,
-        )
-        table = db.create_table("items", pa.table({"id": [1]}))
-
-        ctx = mp.get_context("fork")
-        result_queue = ctx.Queue()
-        process = ctx.Process(
-            target=_direct_namespace_fork_child,
-            args=(table, result_queue),
-        )
-        process.start()
-        process.join(10)
-
-        if process.is_alive():
-            process.terminate()
-            process.join(5)
-            pytest.fail("Direct namespace table hung while reopening after fork")
-
-        assert process.exitcode == 0
-        assert result_queue.get(timeout=2) == ("ok", 1)
-
-    @pytest.mark.skipif(
-        sys.platform != "linux",
-        reason="fork() is only supported safely for this test on Linux",
-    )
-    def test_opaque_direct_namespace_reports_unsupported_fork(self):
-        namespace = namespace_connect("dir", {"root": self.temp_dir})
-        db = lancedb.LanceNamespaceDBConnection(namespace)
-        table = db.create_table("items", pa.table({"id": [1]}))
-
-        with pytest.raises(ValueError, match="opaque namespace client"):
-            db.serialize()
-        assert not table._can_reopen_after_fork
-
-        ctx = mp.get_context("fork")
-        result_queue = ctx.Queue()
-        process = ctx.Process(
-            target=_direct_namespace_fork_child,
-            args=(table, result_queue),
-        )
-        process.start()
-        process.join(10)
-
-        if process.is_alive():
-            process.terminate()
-            process.join(5)
-            pytest.fail("Opaque namespace table hung after fork")
-
-        assert process.exitcode == 0
-        error_type, message = result_queue.get(timeout=2)
-        assert error_type == "RuntimeError"
-        assert "Cannot reopen table 'items' in a forked process" in message
-        assert "namespace_client_impl and namespace_client_properties" in message
+        db.create_table("test_table", schema=schema, storage_options=table_opts)
 
     def test_namespace_operations(self):
         """Test namespace management operations."""

python/python/tests/test_pydantic.py

@@ -415,6 +415,17 @@ def test_nullable_vector():
     assert schema == pa.schema([pa.field("vec", pa.list_(pa.float32(), 16), True)])
 
 
+def test_bare_vector_raises_clear_error():
+    namespace = {
+        "__name__": "test_model_without_pyarrow",
+        "LanceModel": LanceModel,
+        "Vector": Vector,
+    }
+
+    with pytest.raises(TypeError, match=r"Vector must be parameterized.*Vector\(128\)"):
+        exec("class TestModel(LanceModel):\n    vector: Vector", namespace)
+
+
 def test_fixed_size_list_field():
     class TestModel(pydantic.BaseModel):
         vec: Vector(16)

python/python/tests/test_query.py

@@ -570,6 +570,15 @@ def test_query_builder(table):
     assert all(np.array(rs[0]["vector"]) == [1, 2])
 
 
+def test_query_multiple_vectors(table):
+    results = table.search([np.array([1, 2]), np.array([4, 5])]).limit(1).to_list()
+
+    assert len(results) == 2
+    results_by_query = {result["query_index"]: result for result in results}
+    assert results_by_query[0]["id"] == 1
+    assert results_by_query[1]["id"] == 2
+
+
 def test_with_row_id(table: lancedb.table.Table):
     rs = table.search().with_row_id(True).to_arrow()
     assert "_rowid" in rs.column_names

python/python/tests/test_remote_db.py

@@ -2306,3 +2306,79 @@ def test_remote_connection_jobs_surface():
         assert job.status() == "failed"
         with pytest.raises(JobFailedError, match="worker died"):
             job.wait(timeout=timedelta(seconds=5))
+
+
+def test_remote_add_and_list_bases():
+    captured_body = {}
+
+    def handler(request):
+        if request.path == "/v1/table/test/describe/":
+            request.send_response(200)
+            request.send_header("Content-Type", "application/json")
+            request.end_headers()
+            request.wfile.write(json.dumps(BLOB_DESCRIBE_RESPONSE).encode())
+        elif request.path == "/v1/table/test/bases/":
+            content_len = int(request.headers.get("Content-Length", 0))
+            captured_body.update(json.loads(request.rfile.read(content_len)))
+            request.send_response(200)
+            request.send_header("Content-Type", "application/json")
+            request.end_headers()
+            request.wfile.write(b'{"version": 2}')
+        elif request.path == "/v1/table/test/bases/list/":
+            request.send_response(200)
+            request.send_header("Content-Type", "application/json")
+            request.end_headers()
+            request.wfile.write(
+                b'{"bases":[{"path":"s3://bucket/media/","isDatasetRoot":false}]}'
+            )
+        else:
+            request.send_response(404)
+            request.end_headers()
+
+    with mock_lancedb_connection(handler) as db:
+        table = db.open_table("test")
+        table.add_bases(lancedb.TableBase(path="s3://bucket/media/"))
+        assert table.list_bases() == [
+            lancedb.TableBase(
+                path="s3://bucket/media/",
+                name=None,
+                is_dataset_root=False,
+            )
+        ]
+
+    assert captured_body["bases"] == [
+        {
+            "path": "s3://bucket/media/",
+            "isDatasetRoot": False,
+        }
+    ]
+
+
+def test_remote_list_bases_returns_named_dataset_root():
+    def handler(request):
+        if request.path == "/v1/table/test/describe/":
+            request.send_response(200)
+            request.send_header("Content-Type", "application/json")
+            request.end_headers()
+            request.wfile.write(json.dumps(BLOB_DESCRIBE_RESPONSE).encode())
+        elif request.path == "/v1/table/test/bases/list/":
+            request.send_response(200)
+            request.send_header("Content-Type", "application/json")
+            request.end_headers()
+            request.wfile.write(
+                b'{"bases":[{"path":"s3://bucket/archive/","name":"archive","isDatasetRoot":true}]}'
+            )
+        else:
+            request.send_response(404)
+            request.end_headers()
+
+    with mock_lancedb_connection(handler) as db:
+        table = db.open_table("test")
+        assert table.list_bases() == [
+            lancedb.TableBase(
+                path="s3://bucket/archive/",
+                name="archive",
+                is_dataset_root=True,
+            )
+        ]
+

python/python/tests/test_table.py

@@ -2,7 +2,6 @@
 # SPDX-FileCopyrightText: Copyright The LanceDB Authors
 
 
-import asyncio
 import ctypes
 import gc
 import os
@@ -10,7 +9,7 @@ import sys
 import threading
 import warnings
 import weakref
-from concurrent.futures import CancelledError, ThreadPoolExecutor
+from concurrent.futures import ThreadPoolExecutor
 from datetime import date, datetime, timedelta
 from time import sleep
 from typing import List
@@ -930,6 +929,7 @@ def test_polars(mem_db: DBConnection):
 
     # enter table to polars dataframe
     result = table.to_polars()
+    assert isinstance(result, pl.LazyFrame)
     assert np.allclose(result.collect()["vector"].to_list(), data["vector"])
 
     # make sure filtering isn't broken
@@ -1846,6 +1846,27 @@ def test_add_with_empty_fixed_size_list_drops_bad_rows(mem_db: DBConnection):
     assert np.allclose(data["embedding"].to_pylist()[0], np.array([0.1] * 16))
 
 
+def test_add_nullable_fixed_size_list_with_none(mem_db: DBConnection):
+    """Regression test for issue #2340."""
+    table = mem_db.create_table(
+        "test_nullable_fixed_size_list",
+        schema=pa.schema(
+            [
+                pa.field("id", pa.string()),
+                pa.field("feature", pa.list_(pa.float32(), 256)),
+                pa.field("tags", pa.list_(pa.string())),
+            ]
+        ),
+    )
+
+    table.add([{"id": "1", "feature": None, "tags": ["tag1", "tag2"]}])
+
+    result = table.to_arrow()
+    assert result.to_pylist() == [
+        {"id": "1", "feature": None, "tags": ["tag1", "tag2"]}
+    ]
+
+
 def test_add_nullable_struct_with_none(mem_db: DBConnection):
     """Regression test for issue #2654: a nullable struct column whose
     first batch contains only None values must not crash in
@@ -2146,260 +2167,6 @@ def test_restore(mem_db: DBConnection):
         table.restore(0)
 
 
-def test_restore_tracks_checkout_when_restore_fails():
-    class FailingRestore:
-        def __init__(self):
-            self.live_version = None
-
-        async def checkout(self, version):
-            self.live_version = version
-
-        async def restore(self):
-            raise RuntimeError("injected restore failure")
-
-    inner = FailingRestore()
-    table = LanceTable.__new__(LanceTable)
-    table._table = inner
-    table._checkout_version = None
-
-    with pytest.raises(RuntimeError, match="injected restore failure"):
-        table.restore(7)
-
-    assert table._checkout_version == inner.live_version
-
-
-@pytest.mark.parametrize(
-    ("operation", "expected_descriptor", "expected_restore_calls"),
-    [("checkout", 11, 0), ("restore", None, 1)],
-)
-def test_string_tag_resolves_before_checkout(
-    operation, expected_descriptor, expected_restore_calls
-):
-    class Tags:
-        async def get_version(self, tag):
-            assert tag == "tag-v1"
-            return 11
-
-    class NoPostCheckoutVersionLookup:
-        def __init__(self):
-            self.tags = Tags()
-            self.checkout_versions = []
-            self.restore_calls = 0
-
-        async def checkout(self, version):
-            self.checkout_versions.append(version)
-
-        async def version(self):
-            raise RuntimeError("post-checkout version lookup must not run")
-
-        async def restore(self):
-            self.restore_calls += 1
-
-    inner = NoPostCheckoutVersionLookup()
-    table = LanceTable.__new__(LanceTable)
-    table._table = inner
-    table._checkout_version = 3
-
-    getattr(table, operation)("tag-v1")
-
-    assert inner.checkout_versions == [11]
-    assert table._checkout_version == expected_descriptor
-    assert inner.restore_calls == expected_restore_calls
-
-
-@pytest.mark.parametrize("operation", ["checkout", "restore"])
-def test_string_tag_resolution_failure_does_not_mutate_handle(operation):
-    class FailingTags:
-        async def get_version(self, tag):
-            assert tag == "missing-tag"
-            raise RuntimeError("injected tag lookup failure")
-
-    class UnchangedTable:
-        def __init__(self):
-            self.tags = FailingTags()
-            self.checkout_calls = 0
-            self.restore_calls = 0
-
-        async def checkout(self, version):
-            self.checkout_calls += 1
-
-        async def restore(self):
-            self.restore_calls += 1
-
-    inner = UnchangedTable()
-    table = LanceTable.__new__(LanceTable)
-    table._table = inner
-    table._checkout_version = 3
-
-    with pytest.raises(RuntimeError, match="injected tag lookup failure"):
-        getattr(table, operation)("missing-tag")
-
-    assert table._checkout_version == 3
-    assert inner.checkout_calls == 0
-    assert inner.restore_calls == 0
-
-
-def test_native_state_transitions_are_serialized(monkeypatch):
-    from lancedb.background_loop import LOOP
-
-    class Inner:
-        def __init__(self):
-            self.live_version = None
-
-        async def checkout(self, version):
-            self.live_version = version
-
-    inner = Inner()
-    table = LanceTable.__new__(LanceTable)
-    table._table = inner
-    table._checkout_version = None
-
-    first_native_done = threading.Event()
-    release_first_call = threading.Event()
-    second_call_started = threading.Event()
-    second_call_done = threading.Event()
-    errors = []
-    original_run = LOOP.run
-
-    def delayed_delivery(awaitable):
-        result = original_run(awaitable)
-        if threading.current_thread().name == "checkout-1":
-            first_native_done.set()
-            assert release_first_call.wait(5)
-        return result
-
-    monkeypatch.setattr(LOOP, "run", delayed_delivery)
-
-    def checkout(version):
-        if version == 2:
-            second_call_started.set()
-        try:
-            table.checkout(version)
-        except BaseException as err:
-            errors.append(err)
-        finally:
-            if version == 2:
-                second_call_done.set()
-
-    first = threading.Thread(target=checkout, args=(1,), name="checkout-1")
-    first.start()
-    assert first_native_done.wait(5)
-
-    second = threading.Thread(target=checkout, args=(2,), name="checkout-2")
-    second.start()
-    assert second_call_started.wait(5)
-    assert not second_call_done.wait(0.1)
-
-    release_first_call.set()
-    first.join(5)
-    second.join(5)
-
-    assert not first.is_alive()
-    assert not second.is_alive()
-    assert errors == []
-    assert inner.live_version == 2
-    assert table._checkout_version == 2
-
-
-@pytest.mark.parametrize(
-    ("operation", "args", "initial_version", "expected_version"),
-    [
-        ("checkout", (11,), 3, 11),
-        ("checkout_latest", (), 3, None),
-        ("restore", (), 11, None),
-    ],
-)
-def test_native_state_commits_before_success_delivery(
-    monkeypatch, operation, args, initial_version, expected_version
-):
-    from lancedb.background_loop import LOOP
-
-    class Inner:
-        def __init__(self, live_version):
-            self.live_version = live_version
-
-        async def checkout(self, version):
-            self.live_version = version
-
-        async def checkout_latest(self):
-            self.live_version = None
-
-        async def restore(self):
-            self.live_version = None
-
-    inner = Inner(initial_version)
-    table = LanceTable.__new__(LanceTable)
-    table._table = inner
-    table._checkout_version = initial_version
-
-    original_run = LOOP.run
-
-    def success_then_interrupt(awaitable):
-        original_run(awaitable)
-        raise KeyboardInterrupt("injected after native success")
-
-    monkeypatch.setattr(LOOP, "run", success_then_interrupt)
-
-    with pytest.raises(KeyboardInterrupt, match="injected after native success"):
-        getattr(table, operation)(*args)
-
-    assert inner.live_version == expected_version
-    assert table._checkout_version == expected_version
-
-
-def test_native_state_waits_for_cancelled_delivery(monkeypatch):
-    from lancedb.background_loop import LOOP
-
-    class Inner:
-        def __init__(self):
-            self.live_version = 3
-
-        async def checkout(self, version):
-            await asyncio.sleep(0.01)
-            self.live_version = version
-
-    inner = Inner()
-    table = LanceTable.__new__(LanceTable)
-    table._table = inner
-    table._checkout_version = 3
-
-    original_run = LOOP.run
-
-    def cancel_while_running(awaitable):
-        async def cancel_after_start():
-            task = asyncio.create_task(awaitable)
-            await asyncio.sleep(0)
-            task.cancel()
-            return await task
-
-        return original_run(cancel_after_start())
-
-    monkeypatch.setattr(LOOP, "run", cancel_while_running)
-
-    with pytest.raises(CancelledError):
-        table.checkout(11)
-
-    assert inner.live_version == 11
-    assert table._checkout_version == 11
-
-
-def test_reopen_preserves_explicit_table_location(tmp_path):
-    db = lancedb.connect(tmp_path / "db")
-    location = str(tmp_path / "physical-table")
-    table = LanceTable.create(
-        db,
-        "items",
-        pa.table({"x": [1]}),
-        location=location,
-    )
-
-    table._pid = -1
-    table._ensure_open()
-
-    assert table.count_rows() == 1
-    assert table._location == location
-
-
 def test_restore_with_tags(mem_db: DBConnection):
     table = mem_db.create_table(
         "my_table",
@@ -2451,6 +2218,45 @@ def test_merge(tmp_db: DBConnection, tmp_path):
     table.merge(other_dataset, left_on="id")
 
 
+@pytest.mark.parametrize("storage_version", ["legacy", "stable"])
+def test_search_after_merge(tmp_path, storage_version):
+    pytest.importorskip("lance")
+    pd = pytest.importorskip("pandas")
+
+    db = lancedb.connect(
+        tmp_path,
+        storage_options={"new_table_data_storage_version": storage_version},
+    )
+    rng = np.random.default_rng(42)
+    row_count = 512
+    vectors = rng.standard_normal((row_count, 8)).astype(np.float32)
+    table = db.create_table(
+        "search_after_merge",
+        data=pd.DataFrame(
+            {
+                "id": [str(i) for i in range(row_count)],
+                "vector": list(vectors),
+            }
+        ),
+    )
+    table.create_index("vector", config=IvfPq(num_partitions=1, num_sub_vectors=2))
+
+    links = pd.DataFrame(
+        {
+            "id": [str(i) for i in range(row_count // 2)],
+            "link": [f"https://example.com/{i}" for i in range(row_count // 2)],
+        }
+    )
+    table.merge(links, left_on="id")
+
+    query = table.search(vectors[-1]).refine_factor(50).limit(10)
+    assert "ANN" in query.explain_plan(verbose=True)
+
+    result = query.to_arrow()
+    links_by_id = dict(zip(result["id"].to_pylist(), result["link"].to_pylist()))
+    assert links_by_id[str(row_count - 1)] is None
+
+
 def test_delete(mem_db: DBConnection):
     table = mem_db.create_table(
         "my_table",
@@ -2993,15 +2799,40 @@ def test_create_with_embedding_function(mem_db: DBConnection):
     assert actual == expected
 
 
+def test_create_f16_table_from_arrow_data(mem_db: DBConnection):
+    dimension = 32
+    num_rows = 512
+    values = pa.array(
+        np.random.default_rng(42)
+        .standard_normal(num_rows * dimension)
+        .astype(np.float16)
+    )
+    df = pa.table(
+        {
+            "text": [f"s-{i}" for i in range(num_rows)],
+            "vector": pa.FixedSizeListArray.from_arrays(values, dimension),
+        }
+    )
+    table = mem_db.create_table("f16_tbl", data=df)
+    assert table.schema.field("vector").type == pa.list_(pa.float16(), dimension)
+    table.create_index(num_partitions=2, num_sub_vectors=2)
+
+    query = df["vector"][2].as_py()
+    expected = table.search(query).limit(2).to_arrow()
+
+    assert "s-2" in expected["text"].to_pylist()
+
+
 def test_create_f16_table(mem_db: DBConnection):
     class MyTable(LanceModel):
         text: str
         vector: Vector(32, value_type=pa.float16())
 
+    rng = np.random.default_rng(42)
     df = pa.table(
         {
             "text": [f"s-{i}" for i in range(512)],
-            "vector": [np.random.randn(32).astype(np.float16) for _ in range(512)],
+            "vector": [rng.standard_normal(32).astype(np.float16) for _ in range(512)],
         }
     )
     table = mem_db.create_table(
@@ -3882,7 +3713,8 @@ def test_stats(mem_db: DBConnection):
     stats = table.stats()
     print(f"{stats=}")
     assert stats == {
-        "total_bytes": 60,
+        # Full on-disk size of the data file, footer and metadata included.
+        "total_bytes": 633,
         "num_rows": 2,
         "num_indices": 0,
         "fragment_stats": {
@@ -3900,6 +3732,13 @@ def test_stats(mem_db: DBConnection):
         },
     }
 
+    # Index files count toward total_bytes too (only deletion files and
+    # manifests are excluded).
+    table.create_index("id", config=BTree())
+    stats_with_index = table.stats()
+    assert stats_with_index["num_indices"] == 1
+    assert stats_with_index["total_bytes"] > stats["total_bytes"]
+
 
 def test_create_table_empty_list_with_schema(mem_db: DBConnection):
     """Test creating table with empty list data and schema
@@ -4015,3 +3854,65 @@ async def test_async_search_runs_embedding_on_dedicated_executor(
     assert all(name.startswith("lancedb-embedding") for name in captured_threads), (
         f"embedding ran off the dedicated executor: {captured_threads}"
     )
+
+
+def test_computed_column_declare_and_refresh(tmp_path):
+    db = lancedb.connect(tmp_path)
+    table = db.create_table("computed", [{"x": 1}, {"x": 2}])
+
+    table.add_columns(computed={"doubled": "x * 2"})
+    assert table.to_arrow()["doubled"].to_pylist() == [None, None]
+
+    result = table.refresh_column("doubled")
+    assert result.rows_filled == 2
+    assert sorted(table.to_arrow()["doubled"].to_pylist()) == [2, 4]
+
+    table.add([{"x": 5}])
+    assert table.refresh_column("doubled").rows_filled == 1
+    assert sorted(table.to_arrow()["doubled"].to_pylist()) == [2, 4, 10]
+
+
+def test_computed_column_rejects_transforms_and_computed_together(tmp_path):
+    db = lancedb.connect(tmp_path)
+    table = db.create_table("computed_mixed", [{"x": 1}])
+    with pytest.raises(ValueError):
+        table.add_columns({"a": "x + 1"}, computed={"b": "x * 2"})
+
+
+@pytest.mark.asyncio
+async def test_computed_column_async(tmp_path):
+    db = await lancedb.connect_async(tmp_path)
+    table = await db.create_table("computed_async", [{"x": 3}])
+
+    await table.add_columns(computed={"tripled": "x * 3"})
+    await table.refresh_column("tripled")
+
+    assert (await table.to_arrow())["tripled"].to_pylist() == [9]
+
+
+def test_refresh_column_async_returns_job(tmp_path):
+    db = lancedb.connect(tmp_path)
+    table = db.create_table("computed_job", [{"x": 1}, {"x": 2}])
+    table.add_columns(computed={"doubled": "x * 2"})
+
+    job = table.refresh_column_async("doubled")
+    assert job.id is None  # in-process jobs have no server id
+    job.wait()
+    assert job.status() == "finished"
+    assert sorted(table.to_arrow()["doubled"].to_pylist()) == [2, 4]
+
+    # Bad input raises at the call, not through the job.
+    with pytest.raises(Exception, match="not a computed column"):
+        table.refresh_column_async("x")
+
+
+@pytest.mark.asyncio
+async def test_refresh_column_async_job_async_table(tmp_path):
+    db = await lancedb.connect_async(tmp_path)
+    table = await db.create_table("computed_job_async", [{"x": 3}])
+    await table.add_columns(computed={"tripled": "x * 3"})
+
+    job = await table.refresh_column_async("tripled")
+    await job.wait()
+    assert await job.status() == "finished"
+    assert (await table.to_arrow())["tripled"].to_pylist() == [9]

python/python/tests/test_torch.py

@@ -342,42 +342,6 @@ def _multiworker_dataloader_target(db_uri: str, result_queue):
     result_queue.put(count)
 
 
-class _LazyPermutationDataset(torch.utils.data.Dataset):
-    """Match applications that create their Permutation inside a fork worker."""
-
-    def __init__(self, table):
-        self._table = table
-        self._permutation = None
-        self._length = table.count_rows()
-
-    def __len__(self):
-        return self._length
-
-    def __getitems__(self, indices):
-        if self._permutation is None:
-            inherited_connection = self._table._conn
-            self._permutation = Permutation.identity(self._table)
-            if self._table._conn is inherited_connection:
-                raise RuntimeError("Permutation reused a connection inherited by fork")
-        return self._permutation.__getitems__(indices)
-
-
-def _lazy_multiworker_dataloader_target(db_uri: str, result_queue):
-    table = lancedb.connect(db_uri).open_table("test_table")
-    dataset = _LazyPermutationDataset(table)
-    dataloader = torch.utils.data.DataLoader(
-        dataset,
-        batch_size=10,
-        num_workers=2,
-        multiprocessing_context="fork",
-    )
-    count = 0
-    for batch in dataloader:
-        assert batch["a"].size(0) == 10
-        count += 1
-    result_queue.put(count)
-
-
 def _remote_multiworker_dataloader_target(port: int, result_queue):
     import lancedb
     from lancedb.permutation import Permutation
@@ -446,46 +410,6 @@ def test_permutation_dataloader_fork_workers(tmp_path):
     assert queue.get() == 100
 
 
-@pytest.mark.skipif(
-    sys.platform != "linux",
-    reason=(
-        "fork() is unavailable on Windows and unsafe on macOS "
-        "(Apple frameworks/TLS are not fork-safe)"
-    ),
-)
-def test_lazy_permutation_reopens_inherited_table_in_fork_worker(tmp_path):
-    """A lazily built Permutation must not reuse an inherited table client.
-
-    Object-store table handles contain HTTP connection pools that are unsafe
-    after fork. The local table makes the handle replacement deterministic
-    without requiring an S3 service in the unit-test environment.
-    """
-    db_uri = str(tmp_path / "db")
-    db = lancedb.connect(db_uri)
-    db.create_table("test_table", pa.table({"a": list(range(1000))}))
-
-    ctx = mp.get_context("spawn")
-    queue = ctx.Queue()
-    proc = ctx.Process(
-        target=_lazy_multiworker_dataloader_target,
-        args=(db_uri, queue),
-    )
-    proc.start()
-    proc.join(timeout=30)
-
-    if proc.is_alive():
-        proc.terminate()
-        proc.join(timeout=5)
-        if proc.is_alive():
-            proc.kill()
-            proc.join()
-        pytest.fail("Lazy Permutation hung in a fork-based DataLoader worker")
-
-    assert proc.exitcode == 0, f"child exited with code {proc.exitcode}"
-    assert not queue.empty(), "child produced no batches"
-    assert queue.get() == 100
-
-
 @pytest.mark.skipif(
     sys.platform != "linux",
     reason=(

python/python/type_tests/connect.py

@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright The LanceDB Authors
+
+from typing import assert_type
+
+import lancedb
+from lancedb import AsyncConnection, DBConnection
+
+
+def check_connect_type() -> None:
+    assert_type(lancedb.connect("memory://"), DBConnection)
+
+
+async def check_connect_async_type() -> None:
+    assert_type(await lancedb.connect_async("memory://"), AsyncConnection)

python/src/connection.rs

@@ -346,6 +346,23 @@ impl Connection {
         })
     }
 
+    #[pyo3(signature = (name, namespace_path=None))]
+    pub fn drop_table_async(
+        self_: PyRef<'_, Self>,
+        name: String,
+        namespace_path: Option<Vec<String>>,
+    ) -> PyResult<Bound<'_, PyAny>> {
+        let inner = self_.get_inner()?.clone();
+        let ns_path = namespace_path.unwrap_or_default();
+        future_into_py(self_.py(), async move {
+            inner
+                .drop_table_async(name, &ns_path)
+                .await
+                .infer_error()
+                .map(crate::job::Job::new)
+        })
+    }
+
     #[pyo3(signature = (namespace_path=None,))]
     pub fn drop_all_tables(
         self_: PyRef<'_, Self>,

python/src/index.rs

@@ -289,7 +289,7 @@ struct IvfHnswFlatParams {
     target_partition_size: Option<u32>,
 }
 
-#[pyclass(get_all)]
+#[pyclass(module = "lancedb._lancedb", get_all)]
 /// A description of an index currently configured on a column
 pub struct IndexConfig {
     /// The type of the index

python/src/lib.rs

@@ -16,7 +16,8 @@ use query::{FTSQuery, HybridQuery, Query, VectorQuery};
 use session::Session;
 use table::{
     AddColumnsResult, AddResult, AlterColumnsResult, DeleteResult, DropColumnsResult, FtsToken,
-    LsmWriteSpec, MergeResult, PyBlobFile, Table, UpdateFieldMetadataResult, UpdateResult,
+    LsmWriteSpec, MergeResult, PyBlobFile, RefreshColumnResult, Table, UpdateFieldMetadataResult,
+    UpdateResult,
 };
 
 pub mod arrow;
@@ -57,6 +58,7 @@ pub fn _lancedb(_py: Python, m: &Bound<'_, PyModule>) -> PyResult<()> {
     m.add_class::<VectorQuery>()?;
     m.add_class::<RecordBatchStream>()?;
     m.add_class::<AddColumnsResult>()?;
+    m.add_class::<RefreshColumnResult>()?;
     m.add_class::<AlterColumnsResult>()?;
     m.add_class::<UpdateFieldMetadataResult>()?;
     m.add_class::<AddResult>()?;

python/src/session.rs

@@ -11,7 +11,7 @@ use pyo3::{PyResult, pyclass, pymethods};
 /// Sessions allow you to configure cache sizes for index and metadata caches,
 /// which can significantly impact memory use and performance. They can
 /// also be re-used across multiple connections to share the same cache state.
-#[pyclass(from_py_object)]
+#[pyclass(module = "lancedb._lancedb", from_py_object)]
 #[derive(Clone)]
 pub struct Session {
     pub(crate) inner: Arc<LanceSession>,

python/src/table.rs

@@ -22,17 +22,86 @@ use lancedb::index::scalar::FtsIndexBuilder;
 use lancedb::table::{
     AddDataMode, ColumnAlteration, Duration, FieldMetadataUpdate, FtsToken as LanceDbFtsToken,
     NewColumnTransform, OptimizeAction, OptimizeOptions, Ref, Table as LanceDbTable,
+    TableBase as LanceTableBase,
 };
 use lancedb::tokenize as lancedb_tokenize;
 use pyo3::{
     Bound, FromPyObject, Py, PyAny, PyRef, PyResult, Python,
     exceptions::{PyRuntimeError, PyValueError},
     pyclass, pyfunction, pymethods,
-    types::{IntoPyDict, PyAnyMethods, PyBytes, PyDict, PyDictMethods},
+    types::{IntoPyDict, PyAnyMethods, PyBytes, PyDict, PyDictMethods, PyList, PyListMethods},
 };
 
 mod scannable;
 
+/// Convert `LsmStats` to a Python dict, preserving the per-bucket list.
+///
+/// Deliberately not flattened to a table-level summary: a table is N
+/// buckets on one node, and the per-bucket detail is the reason the
+/// endpoint exists — flattening hides the single hot bucket someone opened
+/// it to find.
+fn lsm_stats_to_py(py: Python<'_>, stats: &lancedb::table::LsmStats) -> PyResult<Py<PyDict>> {
+    let out = PyDict::new(py);
+    let buckets = PyList::empty(py);
+    for b in &stats.buckets {
+        let e = PyDict::new(py);
+        e.set_item("shard_id", &b.shard_id)?;
+        e.set_item("status", &b.status)?;
+        e.set_item("writer_epoch", b.writer_epoch)?;
+        e.set_item("manifest_version", b.manifest_version)?;
+        e.set_item("current_generation", b.current_generation)?;
+        e.set_item(
+            "replay_after_wal_entry_position",
+            b.replay_after_wal_entry_position,
+        )?;
+        e.set_item(
+            "wal_entry_position_last_seen",
+            b.wal_entry_position_last_seen,
+        )?;
+
+        let generations = PyList::empty(py);
+        for g in &b.generations {
+            let ge = PyDict::new(py);
+            ge.set_item("generation", g.generation)?;
+            ge.set_item("bytes", g.bytes)?;
+            ge.set_item("rows", g.rows)?;
+            generations.append(ge)?;
+        }
+        e.set_item("generations", generations)?;
+        e.set_item("compacting", b.compacting)?;
+
+        e.set_item(
+            "memtables",
+            b.memtables
+                .as_ref()
+                .map(|ms| {
+                    let l = PyList::empty(py);
+                    for m in ms {
+                        let d = PyDict::new(py);
+                        d.set_item("generation", m.generation)?;
+                        d.set_item("rows", m.rows)?;
+                        d.set_item("bytes", m.bytes)?;
+                        d.set_item("batches", m.batches)?;
+                        d.set_item("indexes", m.indexes.clone())?;
+                        l.append(d)?;
+                    }
+                    PyResult::Ok(l.unbind())
+                })
+                .transpose()?,
+        )?;
+        buckets.append(e)?;
+    }
+    out.set_item("buckets", buckets)?;
+    Ok(out.unbind())
+}
+
+#[derive(FromPyObject)]
+pub(crate) struct PyTableBase {
+    path: String,
+    name: Option<String>,
+    is_dataset_root: bool,
+}
+
 #[derive(FromPyObject)]
 enum PredicateArg {
     Expr(PyExpr),
@@ -185,12 +254,22 @@ impl From<lancedb::table::MergeResult> for MergeResult {
     }
 }
 
+/// Render for `__repr__`, so the default reads as Python's `None` rather than
+/// Rust's `Some([..])`.
+fn fmt_maintained(maintained: &Option<Vec<String>>) -> String {
+    match maintained {
+        Some(names) => format!("{:?}", names),
+        None => "None".to_string(),
+    }
+}
+
 /// Specification selecting Lance's MemWAL LSM-style write path for
 /// `merge_insert`.
 ///
 /// Constructed via the `bucket(...)`, `identity(...)`, or `unsharded()`
 /// classmethods, then optionally chain `with_maintained_indexes(...)` and
-/// `with_writer_config_defaults(...)`.
+/// `with_writer_config_defaults(...)`. A fresh spec maintains every index the
+/// MemWAL supports, resolved on install.
 #[pyclass(from_py_object)]
 #[derive(Clone, Debug)]
 pub struct LsmWriteSpec {
@@ -230,11 +309,11 @@ impl LsmWriteSpec {
         }
     }
 
-    /// Replace the list of indexes the MemWAL should keep up to date as
-    /// rows are appended. Each name must reference an index that
-    /// already exists on the table at the time `set_lsm_write_spec`
-    /// is called.
-    pub fn with_maintained_indexes(&self, indexes: Vec<String>) -> Self {
+    /// Set which indexes the MemWAL maintains. `None` (the default)
+    /// resolves every supported index on install; a list is verbatim,
+    /// and an empty list maintains nothing.
+    #[pyo3(signature = (indexes))]
+    pub fn with_maintained_indexes(&self, indexes: Option<Vec<String>>) -> Self {
         Self {
             inner: self.inner.clone().with_maintained_indexes(indexes),
         }
@@ -256,23 +335,29 @@ impl LsmWriteSpec {
                 maintained_indexes,
                 writer_config_defaults,
             } => format!(
-                "LsmWriteSpec.bucket(column={:?}, num_buckets={}, maintained_indexes={:?}, writer_config_defaults={:?})",
-                column, num_buckets, maintained_indexes, writer_config_defaults,
+                "LsmWriteSpec.bucket(column={:?}, num_buckets={}, maintained_indexes={}, writer_config_defaults={:?})",
+                column,
+                num_buckets,
+                fmt_maintained(maintained_indexes),
+                writer_config_defaults,
             ),
             lancedb::table::LsmWriteSpec::Identity {
                 column,
                 maintained_indexes,
                 writer_config_defaults,
             } => format!(
-                "LsmWriteSpec.identity(column={:?}, maintained_indexes={:?}, writer_config_defaults={:?})",
-                column, maintained_indexes, writer_config_defaults,
+                "LsmWriteSpec.identity(column={:?}, maintained_indexes={}, writer_config_defaults={:?})",
+                column,
+                fmt_maintained(maintained_indexes),
+                writer_config_defaults,
             ),
             lancedb::table::LsmWriteSpec::Unsharded {
                 maintained_indexes,
                 writer_config_defaults,
             } => format!(
-                "LsmWriteSpec.unsharded(maintained_indexes={:?}, writer_config_defaults={:?})",
-                maintained_indexes, writer_config_defaults,
+                "LsmWriteSpec.unsharded(maintained_indexes={}, writer_config_defaults={:?})",
+                fmt_maintained(maintained_indexes),
+                writer_config_defaults,
             ),
         }
     }
@@ -307,10 +392,10 @@ impl LsmWriteSpec {
         }
     }
 
-    /// Names of indexes the MemWAL should keep up to date during writes.
+    /// Indexes the MemWAL keeps up to date, or `None` for every supported one.
     #[getter]
-    pub fn maintained_indexes(&self) -> Vec<String> {
-        self.inner.maintained_indexes().to_vec()
+    pub fn maintained_indexes(&self) -> Option<Vec<String>> {
+        self.inner.maintained_indexes().map(<[String]>::to_vec)
     }
 
     /// Default `ShardWriter` configuration recorded by this spec.
@@ -338,6 +423,32 @@ pub struct AddColumnsResult {
     pub version: u64,
 }
 
+#[pyclass(get_all, from_py_object)]
+#[derive(Clone, Debug)]
+pub struct RefreshColumnResult {
+    pub rows_filled: u64,
+    pub version: u64,
+}
+
+#[pymethods]
+impl RefreshColumnResult {
+    pub fn __repr__(&self) -> String {
+        format!(
+            "RefreshColumnResult(rows_filled={}, version={})",
+            self.rows_filled, self.version
+        )
+    }
+}
+
+impl From<lancedb::table::RefreshColumnResult> for RefreshColumnResult {
+    fn from(result: lancedb::table::RefreshColumnResult) -> Self {
+        Self {
+            rows_filled: result.rows_filled,
+            version: result.version,
+        }
+    }
+}
+
 #[pymethods]
 impl AddColumnsResult {
     pub fn __repr__(&self) -> String {
@@ -502,7 +613,7 @@ impl PyBlobFile {
     }
 }
 
-#[pyclass(get_all, from_py_object)]
+#[pyclass(module = "lancedb._lancedb", get_all, from_py_object)]
 #[derive(Clone, Debug)]
 pub struct FtsToken {
     pub text: String,
@@ -1135,6 +1246,36 @@ impl Table {
         })
     }
 
+    #[pyo3(signature = (bases))]
+    pub fn add_bases(
+        self_: PyRef<'_, Self>,
+        bases: Vec<PyTableBase>,
+    ) -> PyResult<Bound<'_, PyAny>> {
+        let inner = self_.inner_ref()?.clone();
+        let bases: Vec<LanceTableBase> = bases
+            .into_iter()
+            .map(|base| LanceTableBase {
+                path: base.path,
+                name: base.name,
+                is_dataset_root: base.is_dataset_root,
+            })
+            .collect();
+        future_into_py(self_.py(), async move {
+            inner.add_bases(bases).await.infer_error()
+        })
+    }
+
+    pub fn list_bases(self_: PyRef<'_, Self>) -> PyResult<Bound<'_, PyAny>> {
+        let inner = self_.inner_ref()?.clone();
+        future_into_py(self_.py(), async move {
+            let bases = inner.list_bases().await.infer_error()?;
+            Ok(bases
+                .into_iter()
+                .map(|base| (base.path, base.name, base.is_dataset_root))
+                .collect::<Vec<_>>())
+        })
+    }
+
     /// Read blob bytes for `row_ids` from blob v2 column `column`.
     #[pyo3(signature = (column, row_ids))]
     pub fn fetch_blobs(
@@ -1339,6 +1480,51 @@ impl Table {
         })
     }
 
+    /// Converge the table's LSM write path into its base table.
+    ///
+    /// Best-effort: with writes flowing, new rows may land after the last
+    /// pass. Errors if the table stops making progress.
+    pub fn checkpoint_lsm(self_: PyRef<'_, Self>) -> PyResult<Bound<'_, PyAny>> {
+        let inner = self_.inner_ref()?.clone();
+        future_into_py(self_.py(), async move {
+            inner.checkpoint_lsm().await.infer_error()
+        })
+    }
+
+    /// Seal every bucket's active memtable into L0.
+    pub fn flush_lsm(self_: PyRef<'_, Self>) -> PyResult<Bound<'_, PyAny>> {
+        let inner = self_.inner_ref()?.clone();
+        future_into_py(
+            self_.py(),
+            async move { inner.flush_lsm().await.infer_error() },
+        )
+    }
+
+    /// Trigger a background L0 → base pass per bucket. Returns once the
+    /// passes are dispatched, not once they finish — watch `get_lsm_stats`.
+    pub fn compact_lsm(self_: PyRef<'_, Self>) -> PyResult<Bound<'_, PyAny>> {
+        let inner = self_.inner_ref()?.clone();
+        future_into_py(self_.py(), async move {
+            inner.compact_lsm().await.infer_error()
+        })
+    }
+
+    /// Live LSM state, or `None` when the LSM write path is not enabled.
+    #[pyo3(signature = (include_generation_rows=false))]
+    pub fn get_lsm_stats(
+        self_: PyRef<'_, Self>,
+        include_generation_rows: bool,
+    ) -> PyResult<Bound<'_, PyAny>> {
+        let inner = self_.inner_ref()?.clone();
+        future_into_py(self_.py(), async move {
+            let stats = inner
+                .get_lsm_stats(include_generation_rows)
+                .await
+                .infer_error()?;
+            Python::attach(|py| stats.map(|s| lsm_stats_to_py(py, &s)).transpose())
+        })
+    }
+
     pub fn close_lsm_writers(self_: PyRef<'_, Self>) -> PyResult<Bound<'_, PyAny>> {
         let inner = self_.inner_ref()?.clone();
         future_into_py(self_.py(), async move {
@@ -1388,6 +1574,40 @@ impl Table {
         })
     }
 
+    pub fn add_computed_columns(
+        self_: PyRef<'_, Self>,
+        columns: Vec<(String, String)>,
+    ) -> PyResult<Bound<'_, PyAny>> {
+        let inner = self_.inner_ref()?.clone();
+        future_into_py(self_.py(), async move {
+            let mut builder = inner.add_columns();
+            for (name, expression) in columns {
+                builder = builder.computed(name, expression);
+            }
+            let result = builder.execute().await.infer_error()?;
+            Ok(AddColumnsResult::from(result))
+        })
+    }
+
+    pub fn refresh_column(self_: PyRef<'_, Self>, column: String) -> PyResult<Bound<'_, PyAny>> {
+        let inner = self_.inner_ref()?.clone();
+        future_into_py(self_.py(), async move {
+            let result = inner.refresh_column(column).await.infer_error()?;
+            Ok(RefreshColumnResult::from(result))
+        })
+    }
+
+    pub fn refresh_column_async(
+        self_: PyRef<'_, Self>,
+        column: String,
+    ) -> PyResult<Bound<'_, PyAny>> {
+        let inner = self_.inner_ref()?.clone();
+        future_into_py(self_.py(), async move {
+            let job = inner.refresh_column_async(column).await.infer_error()?;
+            Ok(crate::job::Job::new(job))
+        })
+    }
+
     pub fn add_columns_with_schema(
         self_: PyRef<'_, Self>,
         schema: PyArrowType<Schema>,

python/uv.lock

@@ -1998,7 +1998,7 @@ requires-dist = [
     { name = "pillow", marker = "extra == 'clip'", specifier = ">=12.1.1" },
     { name = "pillow", marker = "extra == 'embeddings'", specifier = ">=12.1.1" },
     { name = "pillow", marker = "extra == 'siglip'", specifier = ">=12.1.1" },
-    { name = "polars", marker = "extra == 'tests'", specifier = ">=0.19,<=1.3.0" },
+    { name = "polars", marker = "extra == 'tests'", specifier = ">=0.19,<=1.32.3" },
     { name = "pre-commit", marker = "extra == 'dev'", specifier = ">=3.5.0" },
     { name = "pyarrow", specifier = ">=16" },
     { name = "pyarrow", marker = "extra == 'tests'", specifier = "<25" },

rust/lancedb/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "lancedb"
-version = "0.37.1-beta.0"
+version = "0.38.0-beta.0"
 edition.workspace = true
 description = "LanceDB: A serverless, low-latency vector database for AI applications"
 license.workspace = true
@@ -49,8 +49,6 @@ lance-namespace = { workspace = true }
 lance-namespace-impls = { workspace = true }
 metrics = { workspace = true, optional = true }
 metrics-util = { workspace = true, optional = true }
-# Pin the transitive GooseFS SDK until the 0.1.6 compile break is fixed upstream.
-goosefs-sdk = { version = "=0.1.5", optional = true }
 moka = { workspace = true }
 pin-project = { workspace = true }
 tokio = { version = "1.23", features = ["rt-multi-thread", "sync"] }
@@ -100,7 +98,8 @@ anyhow = "1"
 lance-testing = { workspace = true }
 tempfile = "3.5.0"
 random_word = { version = "0.4.3", features = ["en"] }
-tokio = { version = "1.23", features = ["io-util", "macros", "net", "rt-multi-thread", "sync"] }
+roaring = "0.11.4"
+tokio = { version = "1.23", features = ["io-util", "macros", "net", "rt-multi-thread", "sync", "test-util"] }
 uuid = { version = "1.7.0", features = ["v4"] }
 walkdir = "2"
 aws-sdk-dynamodb = { version = "1.55.0" }
@@ -135,7 +134,6 @@ azure = [
 ]
 cos = ["lance/tencent", "lance-io/tencent"]
 goosefs = [
-    "dep:goosefs-sdk",
     "lance/goosefs",
     "lance-io/goosefs",
     "lance-namespace-impls/dir-goosefs",
@@ -190,6 +188,9 @@ required-features = ["bedrock"]
 [[example]]
 name = "bench_streaming_dataloader"
 
+[[example]]
+name = "bench_open_missing_table"
+
 [[example]]
 name = "simple"
 

rust/lancedb/examples/bench_open_missing_table.rs

@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: Copyright The LanceDB Authors
+
+// Release benchmark for opening a missing table as sibling-table cardinality grows.
+//
+// The fixture uses real `.lance` directories and marker files. Fixture creation is
+// outside the timed section. Defaults intentionally cover 1k, 10k, and 100k siblings
+// with 10 warmups and 100 distinct missing-table opens per scale:
+//
+// ```text
+// cargo run --release -p lancedb --example bench_open_missing_table
+// ```
+//
+// `BENCH_SIBLINGS`, `BENCH_WARMUPS`, and `BENCH_TRIALS` override those defaults.
+// Reduced settings are useful only as a smoke test. Performance comparisons require
+// the same machine, filesystem, fixture sizes, settings, lockfile, and alternating
+// baseline/candidate execution order.
+
+use std::time::{Duration, Instant};
+
+use anyhow::{Context, Result, bail};
+use lancedb::connection::Connection;
+use lancedb::{Error, connect};
+use object_store::ObjectStoreExt as _;
+use object_store::path::Path;
+
+const MAX_SIBLINGS: usize = 1_000_000;
+const MAX_WARMUPS: usize = 10_000;
+const MAX_TRIALS: usize = 100_000;
+
+fn env_usize(key: &str, default: usize, max: usize) -> Result<usize> {
+    let value = match std::env::var(key) {
+        Ok(value) => value
+            .parse()
+            .with_context(|| format!("invalid {key} value: {value}"))?,
+        Err(std::env::VarError::NotPresent) => default,
+        Err(error) => return Err(error).with_context(|| format!("reading {key}")),
+    };
+    if value == 0 || value > max {
+        bail!("{key} must be between 1 and {max}");
+    }
+    Ok(value)
+}
+
+fn sibling_counts() -> Result<Vec<usize>> {
+    let raw = std::env::var("BENCH_SIBLINGS").unwrap_or_else(|_| "1000,10000,100000".into());
+    let mut counts = raw
+        .split(',')
+        .map(|value| {
+            value
+                .trim()
+                .parse::<usize>()
+                .with_context(|| format!("invalid BENCH_SIBLINGS value: {value}"))
+        })
+        .collect::<Result<Vec<_>>>()?;
+    counts.sort_unstable();
+    counts.dedup();
+    if counts.is_empty() || counts[0] == 0 || counts[counts.len() - 1] > MAX_SIBLINGS {
+        bail!("BENCH_SIBLINGS values must be between 1 and {MAX_SIBLINGS}");
+    }
+    Ok(counts)
+}
+
+async fn add_siblings(
+    store: &object_store::local::LocalFileSystem,
+    start: usize,
+    end: usize,
+) -> Result<()> {
+    for index in start..end {
+        let marker = Path::from(format!("sibling_{index:06}.lance/_marker"));
+        store
+            .put(&marker, bytes::Bytes::new().into())
+            .await
+            .with_context(|| format!("creating benchmark marker {marker}"))?;
+    }
+    Ok(())
+}
+
+async fn time_missing_open(db: &Connection, name: &str) -> Result<Duration> {
+    let started = Instant::now();
+    let result = db.open_table(name).execute().await;
+    let elapsed = started.elapsed();
+    match result {
+        Err(Error::TableNotFound { .. }) => Ok(elapsed),
+        Err(error) => bail!("expected TableNotFound for {name}, got {error:?}"),
+        Ok(_) => bail!("benchmark missing-table name unexpectedly exists: {name}"),
+    }
+}
+
+fn percentile(sorted: &[Duration], percentile: usize) -> Duration {
+    let rank = (sorted.len() * percentile).div_ceil(100).saturating_sub(1);
+    sorted[rank]
+}
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    let counts = sibling_counts()?;
+    let warmups = env_usize("BENCH_WARMUPS", 10, MAX_WARMUPS)?;
+    let trials = env_usize("BENCH_TRIALS", 100, MAX_TRIALS)?;
+
+    let fixture = tempfile::tempdir().context("creating benchmark fixture")?;
+    let database_path = fixture.path();
+    let fixture_store = object_store::local::LocalFileSystem::new_with_prefix(database_path)
+        .context("creating benchmark object store")?;
+    let db = connect(database_path.to_str().context("non-UTF-8 fixture path")?)
+        .execute()
+        .await?;
+
+    println!(
+        "config: siblings={counts:?} warmups={warmups} trials={trials} profile={} os={} arch={}",
+        if cfg!(debug_assertions) {
+            "debug"
+        } else {
+            "release"
+        },
+        std::env::consts::OS,
+        std::env::consts::ARCH,
+    );
+    println!("lower is better; fixture setup and teardown are excluded");
+    println!("| siblings | samples | p50 | p95 | max |");
+    println!("| ---: | ---: | ---: | ---: | ---: |");
+
+    let mut created = 0;
+    for sibling_count in counts {
+        add_siblings(&fixture_store, created, sibling_count).await?;
+        created = sibling_count;
+
+        for index in 0..warmups {
+            let name = format!("__missing_warmup_{sibling_count}_{index}");
+            let _ = time_missing_open(&db, &name).await?;
+        }
+
+        let mut samples = Vec::with_capacity(trials);
+        for index in 0..trials {
+            let name = format!("__missing_trial_{sibling_count}_{index}");
+            samples.push(time_missing_open(&db, &name).await?);
+        }
+        samples.sort_unstable();
+
+        println!(
+            "| {sibling_count} | {} | {:?} | {:?} | {:?} |",
+            samples.len(),
+            percentile(&samples, 50),
+            percentile(&samples, 95),
+            samples[samples.len() - 1],
+        );
+    }
+
+    Ok(())
+}

rust/lancedb/src/blob.rs

@@ -17,7 +17,7 @@ use arrow_array::builder::LargeBinaryBuilder;
 use arrow_schema::{DataType, Field, Schema};
 use lance::dataset::{BlobRangeRequest as LanceBlobRangeRequest, Dataset, WriteParams};
 use lance_arrow::FieldExt;
-use lance_encoding::version::LanceFileVersion;
+use lance_file::version::{ConcreteFileVersion, LanceFileVersion};
 use lance_io::object_store::ObjectStore;
 use object_store::path::Path;
 
@@ -333,7 +333,10 @@ pub(crate) fn ensure_blob_storage_version(schema: &Schema, params: &mut WritePar
         .data_storage_version
         .unwrap_or(LanceFileVersion::Stable)
         .resolve();
-    if resolved < LanceFileVersion::V2_2 {
+    if matches!(
+        resolved,
+        ConcreteFileVersion::V1 | ConcreteFileVersion::V2_0 | ConcreteFileVersion::V2_1
+    ) {
         params.data_storage_version = Some(LanceFileVersion::V2_2);
     }
 }
@@ -499,7 +502,7 @@ mod tests {
         ensure_blob_storage_version(&blob_schema(), &mut params);
         assert_eq!(
             params.data_storage_version.unwrap().resolve(),
-            LanceFileVersion::V2_2
+            ConcreteFileVersion::V2_2
         );
     }
 
@@ -512,7 +515,7 @@ mod tests {
         ensure_blob_storage_version(&blob_schema(), &mut params);
         assert_eq!(
             params.data_storage_version.unwrap().resolve(),
-            LanceFileVersion::V2_2
+            ConcreteFileVersion::V2_2
         );
     }
 

rust/lancedb/src/connection.rs

@@ -34,7 +34,7 @@ use crate::remote::{
     db::{OPT_REMOTE_API_KEY, OPT_REMOTE_HOST_OVERRIDE, OPT_REMOTE_REGION},
 };
 use lance::io::ObjectStoreParams;
-pub use lance_encoding::version::LanceFileVersion;
+pub use lance_file::version::LanceFileVersion;
 #[cfg(feature = "remote")]
 use lance_io::object_store::StorageOptions;
 use lance_io::object_store::{StorageOptionsAccessor, StorageOptionsProvider};
@@ -409,6 +409,11 @@ impl Connection {
     ///
     /// The names will be returned in lexicographical order (ascending)
     ///
+    /// Listing databases discover physical `*.lance` entries without opening every
+    /// dataset. The result is a point-in-time discovery snapshot: an entry may still be
+    /// under creation, may contain only uncommitted storage, or may be concurrently
+    /// dropped before it is opened.
+    ///
     /// The parameters `page_token` and `limit` can be used to paginate the results
     pub fn table_names(&self) -> TableNamesBuilder {
         TableNamesBuilder::new(self.internal.clone())
@@ -456,10 +461,9 @@ impl Connection {
     ///
     /// # Returns
     /// Created [`TableRef`], or [`Error::TableNotFound`] if the table does not exist.
-    /// If the table's storage is present but holds no readable dataset (for example a
-    /// `<name>.lance` directory left behind by an interrupted drop and re-create, which
-    /// [`Self::table_names`] still lists) this returns [`Error::TableCorrupted`]
-    /// instead.
+    /// On listing databases, a committed Lance manifest is authoritative for table
+    /// existence. Uncommitted files or a physical `<name>.lance` directory alone do not
+    /// make a table openable.
     pub fn open_table(&self, name: impl Into<String>) -> OpenTableBuilder {
         OpenTableBuilder::new(
             self.internal.clone(),
@@ -561,6 +565,21 @@ impl Connection {
             .await
     }
 
+    /// Start dropping a table and return a handle to the cleanup job.
+    ///
+    /// The table may become unavailable before its physical data is removed.
+    /// Call [`crate::job::Job::wait`] to wait for cleanup to finish. Local
+    /// backends may complete the drop before returning the handle.
+    pub async fn drop_table_async(
+        &self,
+        name: impl AsRef<str>,
+        namespace_path: &[String],
+    ) -> Result<crate::job::Job> {
+        self.internal
+            .drop_table_async(name.as_ref(), namespace_path)
+            .await
+    }
+
     /// Drop the database
     ///
     /// This is the same as dropping all of the tables

rust/lancedb/src/connection/create_table.rs

@@ -438,10 +438,9 @@ mod tests {
             .await
             .unwrap()
             .data_storage_format
-            .lance_file_version()
-            .unwrap();
+            .lance_file_format();
         // Compare resolved versions since Stable/Next are aliases that resolve at storage time
-        assert_eq!(storage_format.resolve(), data_storage_version.resolve());
+        assert_eq!(storage_format, data_storage_version.resolve());
     }
 
     #[tokio::test]

rust/lancedb/src/database.rs

@@ -323,6 +323,18 @@ pub trait Database:
     ) -> Result<()>;
     /// Drop a table in the database
     async fn drop_table(&self, name: &str, namespace_path: &[String]) -> Result<()>;
+    /// Start dropping a table and return a handle to the cleanup job.
+    ///
+    /// Backends without asynchronous cleanup complete the drop before
+    /// returning an already-finished job.
+    async fn drop_table_async(
+        &self,
+        name: &str,
+        namespace_path: &[String],
+    ) -> Result<crate::job::Job> {
+        self.drop_table(name, namespace_path).await?;
+        Ok(crate::job::Job::new_done())
+    }
     /// Drop all tables in the database
     async fn drop_all_tables(&self, namespace_path: &[String]) -> Result<()>;
     fn as_any(&self) -> &dyn std::any::Any;

rust/lancedb/src/database/listing.rs

@@ -12,7 +12,7 @@ use lance::dataset::refs::Ref;
 use lance::dataset::{ReadParams, WriteMode, builder::DatasetBuilder};
 use lance::io::{ObjectStore, ObjectStoreParams, WrappingObjectStore};
 use lance_datafusion::utils::StreamingWriteSource;
-use lance_encoding::version::LanceFileVersion;
+use lance_file::version::LanceFileVersion;
 use lance_io::object_store::{StorageOptionsAccessor, StorageOptionsProvider};
 use lance_table::io::commit::commit_handler_from_url;
 use object_store::local::LocalFileSystem;
@@ -1032,6 +1032,7 @@ impl Database for ListingDatabase {
         };
 
         Ok(ListTablesResponse {
+            context: None,
             tables: f,
             page_token: next_page_token,
         })
@@ -1291,14 +1292,21 @@ impl Database for ListingDatabase {
 mod tests {
     use super::*;
     use crate::Table;
+    use crate::arrow::{SendableRecordBatchStream, SimpleRecordBatchStream};
     use crate::connection::ConnectRequest;
     use crate::data::scannable::Scannable;
     use crate::database::{CreateTableMode, CreateTableRequest};
-    use crate::table::WriteOptions;
+    use crate::query::QueryRequest;
+    use crate::table::{AnyQuery, WriteOptions};
     use arrow_array::{Int32Array, RecordBatch, StringArray};
-    use arrow_schema::{DataType, Field, Schema};
+    use arrow_schema::{DataType, Field, Schema, SchemaRef};
+    use futures::{TryStreamExt, stream::once};
     use std::path::PathBuf;
+    use std::sync::Arc;
+    use std::time::Duration;
     use tempfile::tempdir;
+    use tokio::sync::Barrier;
+    use tokio::time::timeout;
 
     async fn setup_database() -> (tempfile::TempDir, ListingDatabase) {
         let tempdir = tempdir().unwrap();
@@ -1322,6 +1330,114 @@ mod tests {
         (tempdir, db)
     }
 
+    struct BarrierScannable {
+        batch: RecordBatch,
+        barrier: Arc<Barrier>,
+    }
+
+    impl Scannable for BarrierScannable {
+        fn schema(&self) -> SchemaRef {
+            self.batch.schema()
+        }
+
+        fn scan_as_stream(&mut self) -> SendableRecordBatchStream {
+            let batch = self.batch.clone();
+            let schema = batch.schema();
+            let barrier = self.barrier.clone();
+            Box::pin(SimpleRecordBatchStream {
+                schema,
+                stream: once(async move {
+                    barrier.wait().await;
+                    Ok(batch)
+                }),
+            })
+        }
+    }
+
+    fn create_request(name: &str, data: Box<dyn Scannable>) -> CreateTableRequest {
+        CreateTableRequest {
+            name: name.to_string(),
+            namespace_path: vec![],
+            data,
+            mode: CreateTableMode::Create,
+            write_options: Default::default(),
+            location: None,
+            namespace_client: None,
+        }
+    }
+
+    #[tokio::test]
+    async fn test_create_ignores_uncommitted_storage_without_manifest() {
+        let (tmp_dir, db) = setup_database().await;
+        let data_dir = tmp_dir.path().join("test.lance/data");
+        std::fs::create_dir_all(&data_dir).unwrap();
+        std::fs::write(data_dir.join("orphan.lance"), b"uncommitted").unwrap();
+
+        let schema = Arc::new(Schema::new(vec![Field::new("id", DataType::Int32, false)]));
+        let batch =
+            RecordBatch::try_new(schema, vec![Arc::new(Int32Array::from(vec![1]))]).unwrap();
+
+        let table = db
+            .create_table(create_request("test", Box::new(batch)))
+            .await
+            .unwrap();
+        assert_eq!(table.count_rows(None).await.unwrap(), 1);
+    }
+
+    #[tokio::test]
+    async fn test_concurrent_create_is_arbitrated_by_manifest_commit() {
+        let uri = format!("memory:///concurrent-create-{}", uuid::Uuid::new_v4());
+        let db = crate::connect(&uri).execute().await.unwrap();
+        let store: Arc<dyn object_store::ObjectStore> =
+            Arc::new(object_store::memory::InMemory::new());
+        let table_url = url::Url::parse("memory:///database/test.lance").unwrap();
+        let schema = Arc::new(Schema::new(vec![Field::new("id", DataType::Int32, false)]));
+        let batch =
+            RecordBatch::try_new(schema, vec![Arc::new(Int32Array::from(vec![1]))]).unwrap();
+        let barrier = Arc::new(Barrier::new(2));
+
+        #[allow(deprecated)]
+        let request = |batch, barrier| {
+            let mut request = create_request("test", Box::new(BarrierScannable { batch, barrier }));
+            request.write_options = WriteOptions {
+                lance_write_params: Some(lance::dataset::WriteParams {
+                    store_params: Some(ObjectStoreParams {
+                        object_store: Some((store.clone(), table_url.clone())),
+                        ..Default::default()
+                    }),
+                    commit_handler: Some(Arc::new(
+                        lance_table::io::commit::ConditionalPutCommitHandler,
+                    )),
+                    ..Default::default()
+                }),
+            };
+            request
+        };
+
+        let left = db
+            .database()
+            .create_table(request(batch.clone(), barrier.clone()));
+        let right = db.database().create_table(request(batch, barrier));
+        let (left, right) = timeout(Duration::from_secs(30), async { tokio::join!(left, right) })
+            .await
+            .expect("concurrent creates deadlocked");
+
+        let results = [left, right];
+        assert_eq!(
+            results.iter().filter(|result| result.is_ok()).count(),
+            1,
+            "expected one successful create, got {results:?}"
+        );
+        assert_eq!(
+            results
+                .iter()
+                .filter(|result| matches!(result, Err(Error::TableAlreadyExists { .. })))
+                .count(),
+            1,
+            "expected one manifest conflict, got {results:?}"
+        );
+    }
+
     #[tokio::test]
     async fn test_listing_database_root_ops_do_not_create_manifest() {
         let tempdir = tempdir().unwrap();
@@ -1438,6 +1554,94 @@ mod tests {
         assert!(after_open.hits >= before_open.hits + 3);
     }
 
+    /// Regression test for https://github.com/lancedb/lancedb/issues/3197.
+    #[cfg(unix)]
+    #[tokio::test]
+    async fn test_open_table_follows_hugging_face_symlinks() {
+        let (tempdir, db) = setup_database().await;
+        let schema = Arc::new(Schema::new(vec![Field::new("id", DataType::Int32, false)]));
+        db.create_table(CreateTableRequest {
+            name: "test".to_string(),
+            namespace_path: vec![],
+            data: Box::new(
+                RecordBatch::try_new(schema, vec![Arc::new(Int32Array::from(vec![1, 2, 3]))])
+                    .unwrap(),
+            ) as Box<dyn Scannable>,
+            mode: CreateTableMode::Create,
+            write_options: Default::default(),
+            location: None,
+            namespace_client: None,
+        })
+        .await
+        .unwrap();
+
+        let table_dir = tempdir.path().join("test.lance");
+        let versions_dir = table_dir.join("_versions");
+        let manifest_path = std::fs::read_dir(&versions_dir)
+            .unwrap()
+            .map(|entry| entry.unwrap().path())
+            .find(|path| path.extension().is_some_and(|ext| ext == "manifest"))
+            .unwrap();
+        let data_path = std::fs::read_dir(table_dir.join("data"))
+            .unwrap()
+            .map(|entry| entry.unwrap().path())
+            .find(|path| path.extension().is_some_and(|ext| ext == "lance"))
+            .unwrap();
+
+        // Hugging Face snapshots keep dataset objects in a separate blob directory and
+        // expose them through relative symlinks.
+        let blobs_dir = tempdir.path().join("blobs");
+        std::fs::create_dir(&blobs_dir).unwrap();
+        let manifest_blob = "9b603c63d0e692e05d58be25605f2f2064cc781e5ff94fe983a405059547b816";
+        let data_blob = "be64f20e5723bd0a27cfdbdb41cf7d6fad94cd572a71973b717fb8340f4310c5";
+        std::fs::rename(&manifest_path, blobs_dir.join(manifest_blob)).unwrap();
+        std::fs::rename(&data_path, blobs_dir.join(data_blob)).unwrap();
+        std::os::unix::fs::symlink(Path::new("../../blobs").join(manifest_blob), &manifest_path)
+            .unwrap();
+        std::os::unix::fs::symlink(Path::new("../../blobs").join(data_blob), &data_path).unwrap();
+        let symlink_len = std::fs::symlink_metadata(&manifest_path).unwrap().len();
+        let target_len = std::fs::metadata(&manifest_path).unwrap().len();
+        assert_ne!(symlink_len, target_len);
+
+        drop(db);
+        let db = ListingDatabase::connect_with_options(&ConnectRequest {
+            uri: tempdir.path().to_str().unwrap().to_string(),
+            #[cfg(feature = "remote")]
+            client_config: Default::default(),
+            options: Default::default(),
+            namespace_client_properties: Default::default(),
+            manifest_enabled: false,
+            read_consistency_interval: None,
+            session: None,
+        })
+        .await
+        .unwrap();
+
+        let table = db
+            .open_table(OpenTableRequest {
+                name: "test".to_string(),
+                namespace_path: vec![],
+                index_cache_size: None,
+                lance_read_params: None,
+                location: None,
+                namespace_client: None,
+                managed_versioning: None,
+            })
+            .await
+            .unwrap();
+        let batches = table
+            .query(
+                &AnyQuery::Query(QueryRequest::default()),
+                Default::default(),
+            )
+            .await
+            .unwrap()
+            .try_collect::<Vec<_>>()
+            .await
+            .unwrap();
+        assert_eq!(batches.iter().map(RecordBatch::num_rows).sum::<usize>(), 3);
+    }
+
     #[tokio::test]
     async fn test_clone_table_basic() {
         let (_tempdir, db) = setup_database().await;
@@ -2342,7 +2546,7 @@ mod tests {
 
     #[tokio::test]
     async fn test_table_uri() {
-        let (_tempdir, db) = setup_database().await;
+        let (_tempdir, mut db) = setup_database().await;
 
         let mut pb = PathBuf::new();
         pb.push(db.uri.clone());
@@ -2351,6 +2555,18 @@ mod tests {
         let expected = pb.to_str().unwrap();
         let uri = db.table_uri("test").ok().unwrap();
         assert_eq!(uri, expected);
+
+        // URI paths always use forward slashes, even on Windows. Using
+        // `Path::join` here used to produce `az://container/prefix\\test.lance`,
+        // which Azure treated as a different object from the table returned by
+        // `table_names` (https://github.com/lancedb/lancedb/issues/1072).
+        for base_uri in ["az://container/prefix", "az://container/prefix/"] {
+            db.uri = base_uri.to_string();
+            assert_eq!(
+                db.table_uri("test").unwrap(),
+                "az://container/prefix/test.lance"
+            );
+        }
     }
 
     /// Regression: connecting via a URL-style URI (which goes through

rust/lancedb/src/database/namespace.rs

@@ -201,7 +201,7 @@ impl LanceNamespaceDatabase {
         &self,
         request: &DbCreateTableRequest,
     ) -> Result<(
-        Option<lance_encoding::version::LanceFileVersion>,
+        Option<lance_file::version::LanceFileVersion>,
         Option<bool>,
         Option<bool>,
     )> {
@@ -214,7 +214,7 @@ impl LanceNamespaceDatabase {
 
         let storage_version_override = storage_options
             .and_then(|opts| opts.get(OPT_NEW_TABLE_STORAGE_VERSION))
-            .map(|s| s.parse::<lance_encoding::version::LanceFileVersion>())
+            .map(|s| s.parse::<lance_file::version::LanceFileVersion>())
             .transpose()?;
 
         let v2_manifest_override = storage_options

rust/lancedb/src/error.rs

@@ -71,6 +71,14 @@ pub enum Error {
     IndexNotFound { name: String },
     #[snafu(display("Embedding function '{name}' was not found. : {reason}"))]
     EmbeddingFunctionNotFound { name: String, reason: String },
+    #[snafu(display("Column '{name}' was not found"))]
+    ColumnNotFound { name: String },
+    #[snafu(display("Column '{name}' already exists"))]
+    ColumnAlreadyExists { name: String },
+    #[snafu(display("Column '{name}' is not a computed column"))]
+    NotAComputedColumn { name: String },
+    #[snafu(display("Invalid expression for column '{column}': {message}"))]
+    InvalidExpression { column: String, message: String },
 
     #[snafu(display("Table '{name}' already exists"))]
     TableAlreadyExists { name: String },
@@ -169,6 +177,12 @@ impl From<DataFusionError> for Error {
 
 impl From<lance::Error> for Error {
     fn from(source: lance::Error) -> Self {
+        if has_unsupported_local_filesystem_source(&source) {
+            return Self::NotSupported {
+                message: "the filesystem does not support an operation required for safe Lance commits (such as atomic rename). Object-storage mounts such as Mountpoint for Amazon S3 are not supported; use the native object-store URI (for example, s3://bucket/path) instead".to_string(),
+            };
+        }
+
         // Try to unwrap external errors that were wrapped by lance
         match source {
             lance::Error::Wrapped { error, .. } => Self::from_box_error(error),
@@ -181,6 +195,27 @@ impl From<lance::Error> for Error {
     }
 }
 
+fn has_unsupported_local_filesystem_source(error: &(dyn std::error::Error + 'static)) -> bool {
+    let mut current = Some(error);
+    let mut is_local_filesystem = false;
+    let mut is_unsupported = false;
+    while let Some(error) = current {
+        is_local_filesystem |= error
+            .downcast_ref::<object_store::Error>()
+            .is_some_and(|error| {
+                matches!(error, object_store::Error::Generic { store, .. } if *store == "LocalFileSystem")
+            });
+        is_unsupported |= error
+            .downcast_ref::<std::io::Error>()
+            .is_some_and(|error| error.kind() == std::io::ErrorKind::Unsupported);
+        if is_local_filesystem && is_unsupported {
+            return true;
+        }
+        current = error.source();
+    }
+    false
+}
+
 impl Error {
     fn from_box_error(mut source: Box<dyn std::error::Error + Send + Sync>) -> Self {
         source = match source.downcast::<Self>() {
@@ -270,3 +305,46 @@ impl From<candle_core::Error> for Error {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn unsupported_filesystem_operations_have_actionable_error() {
+        let object_store_error = object_store::Error::Generic {
+            store: "LocalFileSystem",
+            source: Box::new(std::io::Error::from(std::io::ErrorKind::Unsupported)),
+        };
+        let lance_error = lance::Error::io_source(Box::new(object_store_error));
+
+        let error = Error::from(lance_error);
+
+        assert!(matches!(
+            error,
+            Error::NotSupported { message }
+                if message.contains("Mountpoint for Amazon S3")
+                    && message.contains("s3://bucket/path")
+        ));
+    }
+
+    #[test]
+    fn other_io_errors_remain_lance_errors() {
+        let object_store_error = object_store::Error::Generic {
+            store: "LocalFileSystem",
+            source: Box::new(std::io::Error::from(std::io::ErrorKind::PermissionDenied)),
+        };
+        let lance_error = lance::Error::io_source(Box::new(object_store_error));
+
+        assert!(matches!(Error::from(lance_error), Error::Lance { .. }));
+    }
+
+    #[test]
+    fn unsupported_non_filesystem_errors_remain_lance_errors() {
+        let lance_error = lance::Error::io_source(Box::new(std::io::Error::from(
+            std::io::ErrorKind::Unsupported,
+        )));
+
+        assert!(matches!(Error::from(lance_error), Error::Lance { .. }));
+    }
+}

rust/lancedb/src/job.rs

@@ -141,7 +141,7 @@ impl SpawnedJob {
                 Ok(Err(err)) => Outcome::Failed(Arc::new(err)),
                 Err(err) if err.is_cancelled() => Outcome::Cancelled,
                 Err(err) => Outcome::Failed(Arc::new(Error::Runtime {
-                    message: format!("index job task failed: {err}"),
+                    message: format!("job task failed: {err}"),
                 })),
             };
             let _ = tx.send(Some(outcome));

rust/lancedb/src/lib.rs

@@ -214,7 +214,7 @@ use lance_linalg::distance::DistanceType as LanceDistanceType;
 /// a built-in pull-based adapter.
 #[cfg(feature = "metrics")]
 pub use metrics;
-pub use table::{FtsToken, Table};
+pub use table::{FtsToken, Table, TableBase};
 
 /// Tokenize a full-text search query using an explicit FTS tokenizer configuration.
 ///

rust/lancedb/src/remote.rs

@@ -19,6 +19,15 @@ const ARROW_FILE_CONTENT_TYPE: &str = "application/vnd.apache.arrow.file";
 #[cfg(test)]
 const JSON_CONTENT_TYPE: &str = "application/json";
 
+fn extract_job_id(body: &str) -> Option<String> {
+    serde_json::from_str::<serde_json::Value>(body)
+        .ok()?
+        .get("job_id")?
+        .as_str()
+        .filter(|job_id| !job_id.is_empty())
+        .map(str::to_string)
+}
+
 pub use client::{ClientConfig, HeaderProvider, RetryConfig, TimeoutConfig, TlsConfig};
 pub use db::{RemoteDatabaseOptions, RemoteDatabaseOptionsBuilder};
 pub use oauth::{OAuthConfig, OAuthFlow, OAuthHeaderProvider};

rust/lancedb/src/remote/db.rs

@@ -9,6 +9,7 @@ use http::StatusCode;
 use lance_io::object_store::StorageOptions;
 use lance_namespace_impls::{DynamicContextProvider, OperationInfo};
 use moka::future::Cache;
+use reqwest::Response;
 use reqwest::header::CONTENT_TYPE;
 
 use lance_namespace::models::{
@@ -23,15 +24,17 @@ use crate::database::{
     JobDescription, JobInfo, OpenTableRequest, ReadConsistency, TableNamesRequest,
 };
 use crate::error::Result;
+use crate::job::Job;
+use crate::remote::job::RemoteJob;
 use crate::remote::util::stream_as_body;
 use crate::table::BaseTable;
 
-use super::ARROW_STREAM_CONTENT_TYPE;
 use super::client::{
     ClientConfig, HeaderProvider, HttpSend, RequestResultExt, RestfulLanceDbClient, Sender,
 };
 use super::table::RemoteTable;
 use super::util::parse_server_version;
+use super::{ARROW_STREAM_CONTENT_TYPE, extract_job_id};
 
 // Request structure for the remote clone table API
 #[derive(serde::Serialize)]
@@ -326,6 +329,22 @@ impl RemoteDatabase {
     }
 }
 
+impl<S: HttpSend> RemoteDatabase<S> {
+    async fn submit_drop_table(
+        &self,
+        name: &str,
+        namespace_path: &[String],
+    ) -> Result<(String, Response)> {
+        let identifier = build_table_identifier(name, namespace_path, &self.client.id_delimiter);
+        let cache_key = build_cache_key(name, namespace_path);
+        let req = self.client.post(&format!("/v1/table/{}/drop/", identifier));
+        let (request_id, resp) = self.client.send(req).await?;
+        let resp = self.client.check_response(&request_id, resp).await?;
+        self.table_cache.remove(&cache_key).await;
+        Ok((request_id, resp))
+    }
+}
+
 #[cfg(all(test, feature = "remote"))]
 mod test_utils {
     use super::*;
@@ -894,13 +913,28 @@ impl<S: HttpSend> Database for RemoteDatabase<S> {
     }
 
     async fn drop_table(&self, name: &str, namespace_path: &[String]) -> Result<()> {
-        let identifier = build_table_identifier(name, namespace_path, &self.client.id_delimiter);
-        let cache_key = build_cache_key(name, namespace_path);
-        let req = self.client.post(&format!("/v1/table/{}/drop/", identifier));
-        let (request_id, resp) = self.client.send(req).await?;
-        self.client.check_response(&request_id, resp).await?;
-        self.table_cache.remove(&cache_key).await;
-        Ok(())
+        self.submit_drop_table(name, namespace_path)
+            .await
+            .map(|_| ())
+    }
+
+    async fn drop_table_async(&self, name: &str, namespace_path: &[String]) -> Result<Job> {
+        let (request_id, response) = self.submit_drop_table(name, namespace_path).await?;
+        let status = response.status();
+        let body = response.text().await.err_to_http(request_id.clone())?;
+        let job_id = extract_job_id(&body);
+        Ok(match job_id {
+            Some(job_id) => Job::new(Box::new(RemoteJob::new(self.client.clone(), job_id))),
+            None if status == StatusCode::ACCEPTED => {
+                return Err(Error::Http {
+                    source: "asynchronous drop-table response did not contain a valid job_id"
+                        .into(),
+                    request_id,
+                    status_code: Some(status),
+                });
+            }
+            None => Job::new_done(),
+        })
     }
 
     async fn drop_all_tables(&self, namespace_path: &[String]) -> Result<()> {
@@ -1492,6 +1526,67 @@ mod tests {
         // NOTE: the API will return 200 even if the table does not exist. So we shouldn't expect 404.
     }
 
+    #[tokio::test]
+    async fn test_drop_table_does_not_read_response_body() {
+        let conn = Connection::new_with_handler(|_| {
+            http::Response::builder()
+                .status(200)
+                .body(vec![0xff])
+                .unwrap()
+        });
+
+        conn.drop_table("table1", &[]).await.unwrap();
+    }
+
+    #[tokio::test]
+    async fn test_drop_table_async_returns_job() {
+        let conn = Connection::new_with_handler(|request| {
+            assert_eq!(request.method(), &reqwest::Method::POST);
+            assert_eq!(request.url().path(), "/v1/table/table1/drop/");
+            http::Response::builder()
+                .status(202)
+                .body(r#"{"job_id":"drop-job-123"}"#)
+                .unwrap()
+        });
+
+        let job = conn.drop_table_async("table1", &[]).await.unwrap();
+        assert_eq!(job.id(), Some("drop-job-123"));
+    }
+
+    #[tokio::test]
+    async fn test_drop_table_async_old_server_returns_done_job() {
+        let conn = Connection::new_with_handler(|_| {
+            http::Response::builder().status(200).body("").unwrap()
+        });
+
+        let job = conn.drop_table_async("table1", &[]).await.unwrap();
+        assert_eq!(job.id(), None);
+        assert_eq!(job.status().await.unwrap(), "finished");
+    }
+
+    #[tokio::test]
+    async fn test_drop_table_async_rejects_accepted_response_without_job_id() {
+        let conn = Connection::new_with_handler(|_| {
+            http::Response::builder().status(202).body("{}").unwrap()
+        });
+
+        let error = conn.drop_table_async("table1", &[]).await.err().unwrap();
+        assert!(error.to_string().contains("valid job_id"));
+    }
+
+    #[tokio::test]
+    async fn test_drop_table_async_rejects_empty_job_id() {
+        let conn = Connection::new_with_handler(|_| {
+            http::Response::builder()
+                .status(202)
+                .body(r#"{"job_id":""}"#)
+                .unwrap()
+        });
+
+        let error = conn.drop_table_async("table1", &[]).await.err().unwrap();
+        assert!(error.to_string().contains("valid job_id"));
+    }
+
     #[tokio::test]
     async fn test_rename_table() {
         let conn = Connection::new_with_handler(|request| {

rust/lancedb/src/remote/table/bases.rs

@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: Copyright The LanceDB Authors
+
+//! Cloud HTTP for registering and listing extra table storage bases.
+
+use serde::Deserialize;
+
+use crate::Error;
+use crate::error::Result;
+use crate::remote::client::{HttpSend, RequestResultExt};
+
+use super::RemoteTable;
+
+#[derive(Debug, Deserialize)]
+struct AddBasesResponse {
+    version: u64,
+}
+
+#[derive(Debug, Deserialize)]
+struct ListBasesResponse {
+    bases: Vec<crate::table::TableBase>,
+}
+
+impl<S: HttpSend> RemoteTable<S> {
+    pub(super) async fn add_bases_impl(&self, bases: &[crate::table::TableBase]) -> Result<()> {
+        self.check_mutable().await?;
+        let mut body = serde_json::json!({ "bases": bases });
+        self.apply_branch_body(&mut body);
+        let request = self
+            .client
+            .post(&format!("/v1/table/{}/bases/", self.identifier))
+            .json(&body);
+        let (request_id, response) = self.send(request, true).await?;
+        let response = self.check_table_response(&request_id, response).await?;
+        let body = response.text().await.err_to_http(request_id.clone())?;
+        let parsed: AddBasesResponse = serde_json::from_str(&body).map_err(|e| Error::Http {
+            source: format!(
+                "The server returned an invalid response while registering table bases: {e}"
+            )
+            .into(),
+            request_id,
+            status_code: None,
+        })?;
+        self.track_write_version(parsed.version);
+        Ok(())
+    }
+
+    pub(super) async fn list_bases_impl(&self) -> Result<Vec<crate::table::TableBase>> {
+        let version = self.current_version().await;
+        let mut body = serde_json::json!({ "version": version });
+        self.apply_branch_body(&mut body);
+        let request = self
+            .post_read(&format!("/v1/table/{}/bases/list/", self.identifier))
+            .json(&body);
+        let (request_id, response) = self.send(request, true).await?;
+        let response = self.check_table_response(&request_id, response).await?;
+        let body = response.text().await.err_to_http(request_id.clone())?;
+        let parsed: ListBasesResponse = serde_json::from_str(&body).map_err(|e| Error::Http {
+            source: format!(
+                "The server returned an invalid response while listing table bases: {e}"
+            )
+            .into(),
+            request_id,
+            status_code: None,
+        })?;
+        Ok(parsed.bases)
+    }
+}

rust/lancedb/src/remote/table/blobs.rs

@@ -90,7 +90,7 @@ struct RemoteBlobState {
 
 /// Seekable Cloud blob handle over HTTP Range.
 #[derive(Debug)]
-pub(crate) struct RemoteBlobFile {
+pub struct RemoteBlobFile {
     requester: Arc<dyn BlobRangeRequester>,
     state: Mutex<RemoteBlobState>,
     closed: AtomicBool,

rust/lancedb/src/remote/table/insert.rs

@@ -33,7 +33,7 @@ use crate::table::{AddResult, MergeResult};
 /// same Arrow-IPC streaming body and error side-channel; only the target
 /// endpoint, query parameters, and parsed result type differ.
 #[derive(Debug, Clone)]
-pub(crate) enum WriteOp {
+pub enum WriteOp {
     /// `add`: stream to `/v1/table/{id}/insert/`, optionally overwriting.
     Insert { overwrite: bool },
     /// `merge_insert`: stream to `/v1/table/{id}/merge_insert/` with the merge
@@ -49,7 +49,7 @@ pub(crate) enum WriteOp {
 /// The parsed server response for a completed write, discriminated by the
 /// operation that produced it.
 #[derive(Debug, Clone)]
-pub(crate) enum WriteResult {
+pub enum WriteResult {
     Add(AddResult),
     Merge(MergeResult),
 }

rust/lancedb/src/table/add_columns.rs

@@ -15,6 +15,7 @@ use crate::{Error, Result};
 pub struct AddColumnsBuilder {
     parent: Arc<dyn BaseTable>,
     transform: Option<NewColumnTransform>,
+    computed: Vec<(String, String)>,
     read_columns: Option<Vec<String>>,
 }
 
@@ -23,6 +24,7 @@ impl std::fmt::Debug for AddColumnsBuilder {
         f.debug_struct("AddColumnsBuilder")
             .field("parent", &self.parent)
             .field("has_transform", &self.transform.is_some())
+            .field("computed", &self.computed)
             .field("read_columns", &self.read_columns)
             .finish()
     }
@@ -33,19 +35,58 @@ impl AddColumnsBuilder {
         Self {
             parent,
             transform: None,
+            computed: Vec::new(),
             read_columns: None,
         }
     }
 
-    /// Set how the new columns' values are produced. Required.
+    /// Set how the new columns' values are produced.
     pub fn transform(mut self, transform: NewColumnTransform) -> Self {
         self.transform = Some(transform);
         self
     }
 
+    /// Add a column defined by `expression`, evaluated by a later refresh
+    /// rather than by this commit. Its type and inputs are derived from the
+    /// expression.
+    ///
+    /// The column is committed with no values, so declaring one costs the same
+    /// on an empty table as on a large one. Rows get values from
+    /// [`Table::refresh_column`](super::Table::refresh_column), which fills
+    /// every fragment that has none -- including fragments appended since the
+    /// last refresh.
+    ///
+    /// Refresh does not revisit a fragment it has filled, so mutating an input
+    /// leaves the value computed at fill time; recomputing means dropping the
+    /// column and declaring it again. An input cannot be renamed, retyped or
+    /// dropped while a declaration reads it, since the expression names it.
+    ///
+    /// On LanceDB Cloud and Enterprise the expression is planned by the
+    /// server, and the refresh runs as a server job -- see
+    /// [`Table::refresh_column_async`](super::Table::refresh_column_async).
+    ///
+    /// ```
+    /// # use lancedb::Table;
+    /// # async fn declare(table: &Table) -> Result<(), Box<dyn std::error::Error>> {
+    /// table
+    ///     .add_columns()
+    ///     .computed("doubled", "x * 2")
+    ///     .execute()
+    ///     .await?;
+    /// let filled = table.refresh_column("doubled").await?;
+    /// println!("filled {} rows", filled.rows_filled);
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn computed(mut self, name: impl Into<String>, expression: impl Into<String>) -> Self {
+        self.computed.push((name.into(), expression.into()));
+        self
+    }
+
     /// Limit which existing columns a [`NewColumnTransform::BatchUDF`] mapper
-    /// receives. Every other transform determines what it reads, so setting
-    /// this alongside one is an error rather than a silent no-op.
+    /// receives. Every other transform, and a computed column, determines what
+    /// it reads, so setting this alongside one is an error rather than a silent
+    /// no-op.
     pub fn read_columns(mut self, columns: impl IntoIterator<Item = impl Into<String>>) -> Self {
         self.read_columns = Some(columns.into_iter().map(Into::into).collect());
         self
@@ -56,24 +97,42 @@ impl AddColumnsBuilder {
         let Self {
             parent,
             transform,
+            computed,
             read_columns,
         } = self;
 
-        let Some(transform) = transform else {
-            return Err(Error::InvalidInput {
-                message: "add_columns requires a transform".into(),
-            });
-        };
-
-        if read_columns.is_some() && !matches!(transform, NewColumnTransform::BatchUDF(_)) {
-            return Err(Error::InvalidInput {
-                message: "read_columns applies only to a BatchUDF transform; \
-                          every other transform determines what it reads"
+        match (transform, computed.is_empty()) {
+            (None, true) => Err(Error::InvalidInput {
+                message: "add_columns requires a transform or a computed column".into(),
+            }),
+            // The two commit through different transforms, so one call covering
+            // both would be two commits and could half-apply.
+            (Some(_), false) => Err(Error::InvalidInput {
+                message: "add_columns cannot mix a transform with computed columns; \
+                          they cannot be added atomically in one call"
                     .into(),
-            });
+            }),
+            (Some(transform), true) => {
+                if read_columns.is_some() && !matches!(transform, NewColumnTransform::BatchUDF(_)) {
+                    return Err(Error::InvalidInput {
+                        message: "read_columns applies only to a BatchUDF transform; \
+                                  every other transform determines what it reads"
+                            .into(),
+                    });
+                }
+                parent.add_columns(transform, read_columns).await
+            }
+            (None, false) => {
+                if read_columns.is_some() {
+                    return Err(Error::InvalidInput {
+                        message: "read_columns applies only to a BatchUDF transform; \
+                                  a computed column's inputs come from its expression"
+                            .into(),
+                    });
+                }
+                parent.add_computed_columns(&computed).await
+            }
         }
-
-        parent.add_columns(transform, read_columns).await
     }
 }
 
@@ -85,8 +144,8 @@ mod tests {
     use arrow_schema::{DataType, Field, Schema};
     use lance::dataset::{BatchUDF, NewColumnTransform};
 
-    use crate::Table;
     use crate::connect;
+    use crate::{Error, Table};
 
     async fn table_with_two_columns(name: &str) -> Table {
         let conn = connect("memory://").execute().await.unwrap();
@@ -98,10 +157,7 @@ mod tests {
     async fn test_requires_a_transform() {
         let table = table_with_two_columns("no_transform").await;
         let err = table.add_columns().execute().await.unwrap_err();
-        assert!(
-            err.to_string().contains("requires a transform"),
-            "got: {err}"
-        );
+        assert!(matches!(err, Error::InvalidInput { .. }));
     }
 
     #[tokio::test]
@@ -117,7 +173,7 @@ mod tests {
             .execute()
             .await
             .unwrap_err();
-        assert!(err.to_string().contains("BatchUDF"), "got: {err}");
+        assert!(matches!(err, Error::InvalidInput { .. }));
 
         let schema = table.schema().await.unwrap();
         assert!(
@@ -126,6 +182,47 @@ mod tests {
         );
     }
 
+    #[tokio::test]
+    async fn test_mixing_transform_and_computed_is_rejected() {
+        let table = table_with_two_columns("mixed_add").await;
+        let err = table
+            .add_columns()
+            .transform(NewColumnTransform::SqlExpressions(vec![(
+                "eager".into(),
+                "x * 2".into(),
+            )]))
+            .computed("lazy", "x * 3")
+            .execute()
+            .await
+            .unwrap_err();
+        assert!(matches!(err, Error::InvalidInput { .. }));
+
+        let schema = table.schema().await.unwrap();
+        assert!(schema.field_with_name("eager").is_err());
+        assert!(schema.field_with_name("lazy").is_err());
+    }
+
+    #[tokio::test]
+    async fn test_read_columns_with_computed_is_rejected() {
+        let table = table_with_two_columns("read_cols_computed").await;
+        let err = table
+            .add_columns()
+            .computed("doubled", "x * 2")
+            .read_columns(["x"])
+            .execute()
+            .await
+            .unwrap_err();
+        assert!(matches!(err, Error::InvalidInput { .. }));
+        assert!(
+            table
+                .schema()
+                .await
+                .unwrap()
+                .field_with_name("doubled")
+                .is_err()
+        );
+    }
+
     #[tokio::test]
     async fn test_read_columns_limits_what_a_batch_udf_sees() {
         let table = table_with_two_columns("read_cols_udf").await;

rust/lancedb/src/table/checkpoint.rs

@@ -0,0 +1,315 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: Copyright The LanceDB Authors
+
+//! Converging a table's LSM write path into its base table.
+//!
+//! `checkpoint_lsm` seals once, then triggers compaction and watches
+//! generation numbers until the L0 that existed at the start is gone.
+//!
+//! The loop runs in the client, not the server: `compact_lsm` dispatches a
+//! pass and returns, so nothing holds a socket and a client can vanish
+//! mid-operation with nothing to reconcile. Completion is read from
+//! generation numbers in the shard manifest — durable state, unlike a count
+//! in a compact response, which a concurrent write invalidates.
+//!
+//! The target set is fixed at the start, so generations created *during* the
+//! checkpoint are ignored. That is what lets it terminate under write load,
+//! and what makes it best-effort: it converges the fresh tier as of some
+//! instant. Idempotent, abandonable at any point, safe on a cadence.
+//!
+//! No liveness bound — the caller owns the deadline. The compactor pool is
+//! shared pod-wide, so a checkpoint queued behind unrelated tables looks
+//! exactly like one that is merging.
+
+use std::collections::HashMap;
+use std::future::Future;
+use std::time::Duration;
+
+use crate::{Error, Result, Table};
+
+/// The HTTP status a failed request carried, if it carried one.
+///
+/// `None` for anything with no retry story: a `TableNotFound` that
+/// `check_table_response` already translated, or a connection failure that
+/// never reached the server. Both are terminal.
+fn status_of(e: &Error) -> Option<u16> {
+    #[cfg(feature = "remote")]
+    {
+        match e {
+            Error::Http {
+                status_code: Some(status),
+                ..
+            } => Some(status.as_u16()),
+            _ => None,
+        }
+    }
+    #[cfg(not(feature = "remote"))]
+    {
+        let _ = e;
+        None
+    }
+}
+
+/// 429 (latch held, pool saturated, or the pod replaying its WAL) and 503 (a
+/// draining node, or a proxy between here and it).
+///
+/// The status is the whole signal: the server deliberately keeps contention
+/// off 503, so a latch collision is a 429. A draining node *is* terminal, but
+/// it is also a 503 that stays a 503, so retrying spends one budget and then
+/// reports the server's own message — cheaper than parsing the body for the
+/// namespace code it would take to tell the two apart.
+fn is_retryable(e: &Error) -> bool {
+    matches!(status_of(e), Some(429 | 503))
+}
+
+/// 421: the owning node holds no claim. Only `flush` re-claims and replays,
+/// so this cannot be retried in place — the caller has to start over.
+fn is_lost_claim(e: &Error) -> bool {
+    status_of(e) == Some(421)
+}
+
+/// Interval between `get_lsm_stats` polls. One interval is roughly one
+/// compaction pass, the granularity at which the answer can change.
+///
+/// Fixed rather than configurable, matching `wait_for_index`. It costs
+/// nothing on an already-converged table and at most one interval of tail
+/// latency after the final pass lands.
+const POLL_INTERVAL: Duration = Duration::from_secs(5);
+
+/// Cap on re-issues from `flush` after a 421, so a crash-looping node cannot
+/// turn flush → compact → 421 → flush into a spin.
+///
+/// Deliberately not shared with [`MAX_RETRIES`]: a claim that keeps
+/// evaporating is a broken node, while contention is routine and wants a real
+/// budget. One shared counter let a merely contended table exhaust this cap
+/// and then blame a claim it never lost.
+const MAX_REISSUES: usize = 3;
+
+/// Retryable faults tolerated on a *single* request, reset on every success —
+/// scattered contention across a long checkpoint must not accumulate toward a
+/// cap. Roughly 16s of retrying against the backoff below.
+const MAX_RETRIES: usize = 8;
+
+/// Backoff between retries, doubling up to [`RETRY_BACKOFF_MAX`]. Latch
+/// contention clears in about the time one pass takes, so start small; a
+/// saturated pool wants the ceiling.
+const RETRY_BACKOFF_BASE: Duration = Duration::from_millis(100);
+const RETRY_BACKOFF_MAX: Duration = Duration::from_secs(5);
+
+/// Sleep before re-issuing a retryable request.
+async fn backoff(attempt: usize) {
+    let delay = RETRY_BACKOFF_BASE
+        .saturating_mul(1u32 << attempt.min(8) as u32)
+        .min(RETRY_BACKOFF_MAX);
+    tokio::time::sleep(delay).await;
+}
+
+/// Whether the drain loop finished or needs the table re-claimed first.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum CheckpointOutcome {
+    Done,
+    ReissueFromFlush,
+}
+
+/// What one LSM request produced: its value, or word that the owning node
+/// holds no claim and only `flush` can get it back.
+enum Attempt<T> {
+    Ok(T),
+    ReissueFromFlush,
+}
+
+/// Issue one LSM request, retrying in place while the fault is retryable.
+///
+/// The two recoverable faults have separate budgets: contention clears on its
+/// own and retries here against [`MAX_RETRIES`], while a 421 needs `flush` to
+/// re-claim, which only the caller can drive.
+///
+/// An exhausted budget propagates the last error *as itself* rather than a
+/// synthesized one — "429 after nine tries" beats "checkpoint failed", and a
+/// draining node arrives carrying the server's own message.
+async fn issue<T, F, Fut>(mut call: F) -> Result<Attempt<T>>
+where
+    F: FnMut() -> Fut,
+    Fut: Future<Output = Result<T>>,
+{
+    let mut retries = 0;
+    loop {
+        let e = match call().await {
+            Ok(value) => return Ok(Attempt::Ok(value)),
+            Err(e) => e,
+        };
+        if is_lost_claim(&e) {
+            return Ok(Attempt::ReissueFromFlush);
+        }
+        if !is_retryable(&e) || retries >= MAX_RETRIES {
+            return Err(e);
+        }
+        backoff(retries).await;
+        retries += 1;
+    }
+}
+
+/// Drive [`Table::checkpoint_lsm`]: seal once, fix the target watermark
+/// from the resulting L0, then trigger and poll until it drains.
+pub(crate) async fn checkpoint_lsm(table: &Table) -> Result<()> {
+    for reissue in 0..=MAX_REISSUES {
+        // The seal turns everything written before this call into a
+        // generation, so the watermark has to be read after it. Idempotent:
+        // sealing an empty memtable is a no-op, so a re-issue does not churn
+        // empty generations.
+        match issue(|| table.flush_lsm()).await? {
+            Attempt::Ok(()) => {}
+            Attempt::ReissueFromFlush => {
+                backoff(reissue).await;
+                continue;
+            }
+        }
+
+        let stats = match issue(|| table.get_lsm_stats(false)).await? {
+            Attempt::Ok(stats) => stats,
+            Attempt::ReissueFromFlush => {
+                backoff(reissue).await;
+                continue;
+            }
+        };
+        let Some(stats) = stats else {
+            // Not WAL-backed; `flush_lsm` would have errored first but for a race.
+            return Ok(());
+        };
+        let targets: HashMap<String, u64> = stats
+            .buckets
+            .iter()
+            .filter_map(|b| Some((b.shard_id.clone(), b.newest_generation()?)))
+            .collect();
+        if targets.is_empty() {
+            return Ok(());
+        }
+
+        match drain_to_targets(table, &targets).await? {
+            CheckpointOutcome::Done => return Ok(()),
+            CheckpointOutcome::ReissueFromFlush => {
+                backoff(reissue).await;
+                continue;
+            }
+        }
+    }
+    Err(Error::Runtime {
+        message: "checkpoint_lsm: the owning node kept losing its claim; \
+                  re-issued from flush the maximum number of times"
+            .into(),
+    })
+}
+
+/// Trigger and poll until no bucket holds a generation at or below its
+/// target.
+///
+/// No liveness bound, deliberately. The pod-wide compactor pool (a semaphore
+/// of 2 by default, shared across every table on the node) is taken *inside*
+/// the pass, after the bucket latch, so a checkpoint queued behind unrelated
+/// tables is indistinguishable from one that is merging. An idle-poll counter
+/// here could only ever have fired on a table that would have finished.
+async fn drain_to_targets(
+    table: &Table,
+    targets: &HashMap<String, u64>,
+) -> Result<CheckpointOutcome> {
+    loop {
+        let stats = match issue(|| table.get_lsm_stats(false)).await? {
+            Attempt::Ok(stats) => stats,
+            Attempt::ReissueFromFlush => return Ok(CheckpointOutcome::ReissueFromFlush),
+        };
+        let Some(stats) = stats else {
+            return Ok(CheckpointOutcome::Done);
+        };
+        // `compacting` is the bucket's compaction latch, held from dispatch
+        // until the pass ends — including while it waits on the pod-wide
+        // permit. So it answers one question only: do not pile on. Buckets
+        // with nothing outstanding are skipped, not counted as idle.
+        let mut outstanding = 0;
+        let mut all_compacting = true;
+        for b in &stats.buckets {
+            let Some(target) = targets.get(&b.shard_id) else {
+                continue;
+            };
+            let n = b.outstanding_generations(*target);
+            if n > 0 {
+                outstanding += n;
+                all_compacting &= b.compacting;
+            }
+        }
+        if outstanding == 0 {
+            return Ok(CheckpointOutcome::Done);
+        }
+
+        if !all_compacting {
+            match table.compact_lsm().await {
+                Ok(()) => {}
+                Err(e) if is_lost_claim(&e) => return Ok(CheckpointOutcome::ReissueFromFlush),
+                Err(e) if !is_retryable(&e) => return Err(e),
+                // A 429 here means the server could latch no bucket at all,
+                // which the poll above already handles. Not retried in place:
+                // the latch it would contend for is the one doing the work, so
+                // fall through and re-read — `POLL_INTERVAL` is the backoff.
+                Err(_) => {}
+            }
+        }
+        tokio::time::sleep(POLL_INTERVAL).await;
+    }
+}
+
+#[cfg(all(test, feature = "remote"))]
+mod tests {
+    use super::*;
+
+    fn http(status: u16) -> Error {
+        Error::Http {
+            source: "server said no".into(),
+            request_id: "rid".into(),
+            status_code: reqwest::StatusCode::from_u16(status).ok(),
+        }
+    }
+
+    /// Every status the loop acts on. The two predicates are checked together
+    /// because their overlap is what would be wrong: a status must never be
+    /// both, and 421 in particular must not read as retryable — retrying it in
+    /// place re-issues the call that just said the node holds no claim.
+    #[test]
+    fn taxonomy_round_trips() {
+        for status in [429, 503] {
+            assert!(is_retryable(&http(status)), "{status} must retry");
+            assert!(
+                !is_lost_claim(&http(status)),
+                "{status} is not a lost claim"
+            );
+        }
+        assert!(is_lost_claim(&http(421)), "a lost claim must re-claim");
+        assert!(
+            !is_retryable(&http(421)),
+            "retrying a lost claim in place only asks the same node again"
+        );
+        for status in [400, 404, 409, 500] {
+            assert!(!is_retryable(&http(status)), "{status} is terminal");
+            assert!(!is_lost_claim(&http(status)), "{status} is terminal");
+        }
+    }
+
+    /// An error carrying no status has no retry story and must be terminal —
+    /// a connection that never reached the server, or a `TableNotFound` that
+    /// `check_table_response` translated before the loop saw it.
+    #[test]
+    fn errors_without_a_status_are_terminal() {
+        let no_status = Error::Http {
+            source: "connection reset".into(),
+            request_id: "rid".into(),
+            status_code: None,
+        };
+        assert!(!is_retryable(&no_status));
+        assert!(!is_lost_claim(&no_status));
+
+        let translated = Error::TableNotFound {
+            name: "t".into(),
+            source: "gone".into(),
+        };
+        assert!(!is_retryable(&translated));
+        assert!(!is_lost_claim(&translated));
+    }
+}

rust/lancedb/src/table/datafusion/insert.rs

@@ -17,7 +17,7 @@ use datafusion_physical_plan::stream::RecordBatchStreamAdapter;
 use datafusion_physical_plan::{
     DisplayAs, DisplayFormatType, ExecutionPlan, ExecutionPlanProperties, PlanProperties,
 };
-use futures::TryStreamExt;
+use futures::StreamExt;
 use lance::Dataset;
 use lance::dataset::transaction::{Operation, Transaction};
 use lance::dataset::{CommitBuilder, InsertBuilder, WriteParams, WriteProgressFn};
@@ -194,12 +194,23 @@ impl ExecutionPlan for InsertExec {
 
         let output_bytes = MetricBuilder::new(&self.metrics).output_bytes(partition);
         let input_schema = input_stream.schema();
+        let declared: Vec<String> = crate::table::computed_columns::computed_columns(
+            &arrow_schema::Schema::from(self.dataset.schema()),
+        )
+        .into_iter()
+        .map(|declaration| declaration.name)
+        .collect();
         let input_stream: SendableRecordBatchStream =
             Box::pin(InstrumentedRecordBatchStreamAdapter::new(
                 input_schema,
-                input_stream.map_ok(move |batch| {
+                input_stream.map(move |batch| {
+                    let batch = batch?;
+                    crate::table::computed_columns::ensure_batch_writes_no_computed_values(
+                        &declared, &batch,
+                    )
+                    .map_err(|e| datafusion::error::DataFusionError::External(Box::new(e)))?;
                     output_bytes.add(batch.get_array_memory_size());
-                    batch
+                    Ok(batch)
                 }),
                 partition,
                 &self.metrics,

rust/lancedb/src/table/lsm_stats.rs

@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: Apache-2.0
+// SPDX-FileCopyrightText: Copyright The LanceDB Authors
+
+//! Live per-bucket LSM state — the shape [`crate::Table::get_lsm_stats`]
+//! returns and [`super::checkpoint`] polls.
+//!
+//! Nothing here is derived: sums and differences (total L0 bytes, WAL lag)
+//! are the caller's to compute. There is no "WAL is off" shape — that case is
+//! `None`, because a struct of zeros would read as measurements.
+
+use serde::Deserialize;
+
+/// One flushed L0 generation.
+#[derive(Debug, Clone, Deserialize)]
+pub struct GenerationStats {
+    pub generation: u64,
+    pub bytes: u64,
+    /// Present only when `include_generation_rows` was requested. Off by
+    /// default because each count opens an uncached Lance dataset, and the
+    /// checkpoint loop polls this route needing only generation numbers.
+    #[serde(default)]
+    pub rows: Option<u64>,
+}
+
+/// One in-memory memtable.
+#[derive(Debug, Clone, Deserialize)]
+pub struct MemtableStats {
+    pub generation: u64,
+    pub rows: u64,
+    pub bytes: u64,
+    pub batches: u64,
+    /// Names of the indexes this memtable carries. An absent name is the whole
+    /// answer to "why is my fresh-tier search on that column brute-force".
+    pub indexes: Vec<String>,
+}
+
+/// Live state of one bucket. A table is N buckets on one node; flattening to
+/// a single number hides the one hot bucket that is usually why someone
+/// opened this endpoint.
+#[derive(Debug, Clone, Deserialize)]
+pub struct BucketStats {
+    pub shard_id: String,
+    /// `Active` | `Sealed` (drop-table 2PC in flight).
+    pub status: String,
+    pub writer_epoch: u64,
+    pub manifest_version: u64,
+    pub current_generation: u64,
+    pub replay_after_wal_entry_position: u64,
+    pub wal_entry_position_last_seen: u64,
+    pub generations: Vec<GenerationStats>,
+    /// Whether a pass owns this bucket's compaction latch right now. Says *a*
+    /// driver is running, not *whose*, and the latch is held from dispatch —
+    /// including while the pass queues for a pod-wide compactor permit. Read
+    /// it as "do not pile on", never as "mine is progressing".
+    pub compacting: bool,
+    /// Oldest first, active last. Absent for a `Sealed` bucket, whose
+    /// in-memory state is torn down.
+    #[serde(default)]
+    pub memtables: Option<Vec<MemtableStats>>,
+}
+
+impl BucketStats {
+    /// The newest flushed generation, or `None` when L0 is empty.
+    pub(crate) fn newest_generation(&self) -> Option<u64> {
+        self.generations.iter().map(|g| g.generation).max()
+    }
+
+    /// How many generations at or below `target` are still in L0.
+    ///
+    /// A count, not a boolean: one pass drains a bounded prefix rather than
+    /// the whole target set, so a boolean would read as "no progress" for
+    /// every pass but the last. Compaction drains oldest-first, so this
+    /// decreases monotonically.
+    pub(crate) fn outstanding_generations(&self, target: u64) -> usize {
+        self.generations
+            .iter()
+            .filter(|g| g.generation <= target)
+            .count()
+    }
+}
+
+/// Live LSM state, one entry per bucket.
+#[derive(Debug, Clone, Deserialize)]
+pub struct LsmStats {
+    pub buckets: Vec<BucketStats>,
+}
+
+/// Server-side JSON envelope for `get_lsm_stats`. `lsm_stats` is null when
+/// the table has no LSM write path.
+#[derive(Debug, Deserialize)]
+pub(crate) struct GetLsmStatsResponse {
+    #[serde(default)]
+    pub lsm_stats: Option<LsmStats>,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn bucket(shard: &str, generations: &[u64], compacting: bool) -> BucketStats {
+        BucketStats {
+            shard_id: shard.into(),
+            status: "Active".into(),
+            writer_epoch: 1,
+            manifest_version: 1,
+            current_generation: generations.iter().max().copied().unwrap_or(0) + 1,
+            replay_after_wal_entry_position: 0,
+            wal_entry_position_last_seen: 0,
+            generations: generations
+                .iter()
+                .map(|g| GenerationStats {
+                    generation: *g,
+                    bytes: 1,
+                    rows: None,
+                })
+                .collect(),
+            compacting,
+            memtables: None,
+        }
+    }
+
+    /// The target watermark is the newest generation at the start, and a
+    /// generation created after it must not hold the loop open — that is why
+    /// the predicate terminates under write load.
+    #[test]
+    fn newer_generations_do_not_extend_the_target() {
+        let start = bucket("b0", &[7, 8], false);
+        let target = start.newest_generation().expect("L0 is non-empty");
+        assert_eq!(target, 8);
+
+        // Compaction drained 7 and 8; 9 and 10 arrived while it ran.
+        let later = bucket("b0", &[9, 10], false);
+        assert_eq!(
+            later.outstanding_generations(target),
+            0,
+            "generations above the target are somebody else's problem"
+        );
+
+        // Still holding 8 means still outstanding.
+        assert_eq!(
+            bucket("b0", &[8, 9], false).outstanding_generations(target),
+            1
+        );
+    }
+
+    /// The metric counts generations, not buckets: a pass drains a bounded
+    /// prefix, so one bucket going 3 → 2 → 1 → 0 is three steps.
+    #[test]
+    fn progress_is_measured_in_generations() {
+        let target = 3;
+        let counts: Vec<usize> = [&[1u64, 2, 3][..], &[2, 3][..], &[3][..], &[][..]]
+            .iter()
+            .map(|gens| bucket("b0", gens, false).outstanding_generations(target))
+            .collect();
+        assert_eq!(counts, vec![3, 2, 1, 0]);
+    }
+
+    #[test]
+    fn empty_l0_has_no_target() {
+        assert!(bucket("b0", &[], false).newest_generation().is_none());
+    }
+}

rust/lancedb/src/table/merge.rs

@@ -1161,7 +1161,7 @@ mod lsm_tests {
             .unwrap();
         let fts_index = table.list_indices().await.unwrap()[0].name.clone();
         table
-            .set_lsm_write_spec(LsmWriteSpec::unsharded().with_maintained_indexes([fts_index]))
+            .set_lsm_write_spec(LsmWriteSpec::unsharded().with_maintained_indexes(vec![fts_index]))
             .await
             .unwrap();
 
@@ -1254,7 +1254,7 @@ mod lsm_tests {
             .unwrap();
         let vec_index = table.list_indices().await.unwrap()[0].name.clone();
         table
-            .set_lsm_write_spec(LsmWriteSpec::unsharded().with_maintained_indexes([vec_index]))
+            .set_lsm_write_spec(LsmWriteSpec::unsharded().with_maintained_indexes(vec![vec_index]))
             .await
             .unwrap();
 

rust/lancedb/src/table/merge/lsm.rs

@@ -29,6 +29,7 @@ use arrow_schema::{DataType, Schema as ArrowSchema, SchemaRef};
 use lance::Dataset;
 use lance::dataset::mem_wal::{
     DatasetMemWalExt, ShardWriter, ShardWriterConfig, evaluate_sharding_spec,
+    validate_maintained_indexes,
 };
 use lance::index::DatasetIndexExt;
 use lance_core::datatypes::Schema as LanceSchema;
@@ -37,8 +38,9 @@ use tokio::sync::RwLock;
 use uuid::Uuid;
 
 use crate::error::{Error, Result};
+use crate::index::IndexConfig;
 use crate::table::merge::{MergeInsertBuilder, MergeResult};
-use crate::table::{LsmWriteSpec, NativeTable};
+use crate::table::{BaseTable, LsmWriteSpec, NativeTable};
 
 /// Spec id of the sole sharding spec installed by [`set_lsm_write_spec`].
 /// Must match Lance's `InitializeMemWalBuilder` (`SHARDING_SPEC_ID`).
@@ -80,32 +82,53 @@ pub(crate) async fn set_lsm_write_spec(table: &NativeTable, spec: LsmWriteSpec)
         }
     }
 
+    // Before the builder borrows the dataset clone. `list_indices` merges an
+    // index's segments into one entry, so the result needs no dedup.
+    let maintained_indexes = {
+        let dataset = table.dataset.get().await?;
+        resolve_maintained_indexes(
+            &dataset,
+            &table.list_indices().await?,
+            spec.maintained_indexes(),
+        )
+        .await?
+    };
+
+    table.checkout_latest().await?;
     let mut dataset = (*table.dataset.get().await?).clone();
+    let schema = arrow_schema::Schema::from(dataset.schema());
+    if !crate::table::computed_columns::computed_columns(&schema).is_empty() {
+        return Err(Error::NotSupported {
+            message: "an LSM write spec cannot be installed on a table with computed \
+                      columns: rows in un-compacted tiers are invisible to refresh"
+                .into(),
+        });
+    }
     let mut builder = dataset.initialize_mem_wal();
-    let (maintained_indexes, writer_config_defaults) = match spec {
+    let writer_config_defaults = match spec {
         LsmWriteSpec::Bucket {
             column,
             num_buckets,
-            maintained_indexes,
             writer_config_defaults,
+            ..
         } => {
             builder = builder.bucket_sharding(column, num_buckets);
-            (maintained_indexes, writer_config_defaults)
+            writer_config_defaults
         }
         LsmWriteSpec::Identity {
             column,
-            maintained_indexes,
             writer_config_defaults,
+            ..
         } => {
             builder = builder.identity_sharding(column);
-            (maintained_indexes, writer_config_defaults)
+            writer_config_defaults
         }
         LsmWriteSpec::Unsharded {
-            maintained_indexes,
             writer_config_defaults,
+            ..
         } => {
             builder = builder.unsharded();
-            (maintained_indexes, writer_config_defaults)
+            writer_config_defaults
         }
     };
     builder = builder.maintained_indexes(maintained_indexes);
@@ -117,6 +140,88 @@ pub(crate) async fn set_lsm_write_spec(table: &NativeTable, spec: LsmWriteSpec)
     Ok(())
 }
 
+/// Resolve a spec's maintained-index selection against `indices`, as reported
+/// by [`Table::list_indices`](crate::Table::list_indices).
+///
+/// `None` means every index on the table, snapshotted now. Lance validates
+/// either selection against its shard-writer rules, so a spec that installs is
+/// one the MemWAL can open.
+///
+/// An unmaintainable index fails an inferred set rather than being dropped from
+/// it — dropping would leave the caller believing it is maintained.
+async fn resolve_maintained_indexes(
+    dataset: &Dataset,
+    indices: &[IndexConfig],
+    requested: Option<&[String]>,
+) -> Result<Vec<String>> {
+    let Some(requested) = requested else {
+        let all: Vec<String> = indices.iter().map(|index| index.name.clone()).collect();
+        validate_maintained_indexes(dataset, &all)
+            .await
+            .map_err(|source| Error::InvalidInput {
+                message: format!(
+                    "cannot maintain every index on this table: {source}. Set \
+                     maintained_indexes explicitly to choose from {}",
+                    index_name_list(indices),
+                ),
+            })?;
+        return Ok(all);
+    };
+    for name in requested {
+        if !indices.iter().any(|index| &index.name == name) {
+            return Err(Error::InvalidInput {
+                message: format!(
+                    "maintained index '{}' does not exist on this table; it has {}",
+                    name,
+                    index_name_list(indices),
+                ),
+            });
+        }
+    }
+    validate_maintained_indexes(dataset, requested).await?;
+    Ok(requested.to_vec())
+}
+
+/// Index names for an error message.
+fn index_name_list(indices: &[IndexConfig]) -> String {
+    if indices.is_empty() {
+        return "no indexes".to_string();
+    }
+    let mut names: Vec<&str> = indices.iter().map(|index| index.name.as_str()).collect();
+    names.sort_unstable();
+    format!("[{}]", names.join(", "))
+}
+
+// =============================================================================
+// require_mem_wal_index_catchup
+// =============================================================================
+
+/// Switch this table to required index catch-up, one way.
+///
+/// Deliberately **not** part of installing the write spec. Until something can
+/// actually repair coverage, a table carrying the bit reports every index as
+/// not known to hold the compacted rows, so its SSTables are retained
+/// indefinitely -- and the WAL pod trims on the legacy rule meanwhile, leaving
+/// readers pointed at files that are gone. Turn this on only once remote
+/// maintenance owns the merge and the repair for the table.
+///
+/// Lance refuses the activation if the table already records SSTable
+/// compaction progress: those numbers predate this protocol and cannot be
+/// validated, so such a table must be drained rather than activated.
+#[allow(clippy::redundant_pub_crate)]
+pub(crate) async fn require_mem_wal_index_catchup(table: &NativeTable) -> Result<()> {
+    table.dataset.ensure_mutable()?;
+    let mut dataset = (*table.dataset.get().await?).clone();
+    if dataset.mem_wal_index_details().await?.is_none() {
+        return Err(Error::InvalidInput {
+            message: "require_mem_wal_index_catchup: no LSM write spec is set on this table".into(),
+        });
+    }
+    dataset.require_mem_wal_index_catchup().await?;
+    table.dataset.update(dataset);
+    Ok(())
+}
+
 // =============================================================================
 // unset_lsm_write_spec
 // =============================================================================

rust/lancedb/src/table/query/lsm.rs

@@ -36,6 +36,7 @@ use lance::dataset::mem_wal::{
     DatasetMemWalExt, LsmScanner, ShardManifestStore, ShardSnapshot, ShardWriterConfig,
 };
 use lance_index::mem_wal::{MemWalIndexDetails, ShardManifest};
+use lance_table::feature_flags::FLAG_MEM_WAL_INDEX_CATCHUP;
 use uuid::Uuid;
 
 use super::NativeTable;
@@ -84,9 +85,8 @@ pub(super) async fn create_lsm_plan(
     let pk_columns = pk_columns(&ds_ref)?;
     // The base index an indexed arm relies on may lag compaction; resolve it so the
     // snapshot retains SSTables the index has not yet caught up to.
-    let arm_index = arm_maintained_index_name(&ds_ref, &query, &details).await?;
-    let (snapshots, in_memory) =
-        build_read_context(table, &ds_ref, &details, arm_index.as_deref()).await?;
+    let arm_indexes = arm_maintained_index_names(&ds_ref, &query, &details).await?;
+    let (snapshots, in_memory) = build_read_context(table, &ds_ref, &details, &arm_indexes).await?;
 
     let limit = query.base.limit;
     let offset = query.base.offset;
@@ -232,28 +232,44 @@ fn pk_columns(dataset: &Dataset) -> Result<Vec<String>> {
     Ok(pk)
 }
 
-/// Per-shard SSTable exclusion watermark: the generation at or below which SSTables
-/// are safe to drop for this arm. A generation is droppable only once it is
-/// compacted into the base table AND covered by `index_name`'s catch-up (for an
-/// indexed arm); a plain scan (`index_name == None`) uses the compaction watermark
-/// alone. Capping at the index catch-up keeps rows the base index has not yet
-/// indexed visible through their SSTable. First occurrence per shard mirrors Lance's
-/// `compacted_generation_for_shard`.
+/// Per-shard SSTable exclusion watermark: the generation at or below which
+/// SSTables are safe to drop for this query.
+///
+/// A generation is droppable only once it is compacted into the base table AND
+/// covered by the catch-up of every index the query relies on, so the watermark
+/// is the minimum across `index_names`. Gating on fewer than all of them would
+/// drop SSTables holding rows an uncounted index has not yet indexed, and that
+/// arm would silently return fewer rows.
+///
+/// See [`arm_maintained_index_names`] for which indexes are collected today: a
+/// vector search with a scalar prefilter is not yet among them.
+///
+/// An empty `index_names` (a plain scan) uses the compaction watermark alone.
+/// First occurrence per shard mirrors Lance's `compacted_generation_for_shard`.
 fn exclusion_watermarks(
     details: &MemWalIndexDetails,
-    index_name: Option<&str>,
+    index_names: &[String],
+    catchup_required: bool,
 ) -> HashMap<Uuid, u64> {
     let mut exclude: HashMap<Uuid, u64> = HashMap::new();
     for entry in &details.compacted_sstables {
         let mut watermark = entry.generation;
-        if let Some(name) = index_name
-            && let Some(caught_up) = details
+        for name in index_names {
+            match details
                 .index_catchup
                 .iter()
-                .find(|icp| icp.index_name == name)
+                .find(|icp| icp.index_name == *name)
                 .and_then(|icp| icp.caught_up_generation_for_shard(&entry.shard_id))
-        {
-            watermark = watermark.min(caught_up);
+            {
+                Some(caught_up) => watermark = watermark.min(caught_up),
+                // No entry. On a table that requires catch-up this means the
+                // index is *not* known to hold these rows, and the base arm is
+                // index-only -- so every generation stays readable from its
+                // SSTable. Without the bit the field is not maintained at all,
+                // and absence carries no information.
+                None if catchup_required => watermark = 0,
+                None => {}
+            }
         }
         exclude.entry(entry.shard_id).or_insert(watermark);
     }
@@ -267,13 +283,26 @@ fn exclusion_watermarks(
 /// with a live cached `ShardWriter` (this session's in-flight writes) the
 /// writer's authoritative in-memory manifest and memtables override the
 /// on-disk view so a read sees data not yet flushed.
+/// Whether this table reads a missing `index_catchup` entry as "not caught up".
+///
+/// Both words must be set. A reader honouring the bit while a writer does not
+/// would retain SSTables the writer had already trimmed, and the reverse would
+/// serve rows from files the writer still expects to be excluded -- so a
+/// half-set manifest is treated as legacy, which is the conservative side.
+fn requires_index_catchup(dataset: &Dataset) -> bool {
+    let manifest = dataset.manifest();
+    manifest.reader_feature_flags & FLAG_MEM_WAL_INDEX_CATCHUP != 0
+        && manifest.writer_feature_flags & FLAG_MEM_WAL_INDEX_CATCHUP != 0
+}
+
 async fn build_read_context(
     table: &NativeTable,
     dataset: &Dataset,
     details: &MemWalIndexDetails,
-    index_name: Option<&str>,
+    index_names: &[String],
 ) -> Result<(Vec<ShardSnapshot>, HashMap<Uuid, InMemoryMemTables>)> {
-    let exclude = exclusion_watermarks(details, index_name);
+    let catchup_required = requires_index_catchup(dataset);
+    let exclude = exclusion_watermarks(details, index_names, catchup_required);
 
     let shard_ids = dataset.list_mem_wal_latest_shard_ids().await?;
     // Use the dataset's own object store (not `ObjectStore::from_uri`, which
@@ -487,19 +516,33 @@ async fn index_maintained(
     }))
 }
 
-/// The maintained base index the query's arm relies on (vector index for ANN, FTS
-/// index for full-text), used to gate SSTable compaction exclusion by index catch-up.
-/// `None` for a plain scan or when no maintained index covers the searched column.
-async fn arm_maintained_index_name(
+/// Every maintained base index this query relies on, used to gate SSTable
+/// exclusion by index catch-up.
+///
+/// Returns a list because the watermark must be the lowest across every index a
+/// query relies on. Today it never holds more than one: `reject_unsupported`
+/// refuses hybrid search, so the vector and full-text arms are mutually
+/// exclusive.
+///
+/// The case that is genuinely multi-index -- a vector search with a scalar or
+/// bitmap prefilter -- is **not collected yet**. Identifying those needs the
+/// planner's chosen indexes, not the columns the filter names, and no Lance API
+/// exposes them. Until it does, such a query is gated on its vector index alone.
+///
+/// Empty for a plain scan, or when no maintained index covers the searched
+/// column.
+async fn arm_maintained_index_names(
     dataset: &Dataset,
     query: &VectorQueryRequest,
     details: &MemWalIndexDetails,
-) -> Result<Option<String>> {
+) -> Result<Vec<String>> {
     use lance::index::DatasetIndexExt;
-    // Resolve the arm's searched column, the index-detail type it relies on, and a
+
+    // Each arm's searched column, the index-detail type it relies on, and a
     // label for diagnostics — catch-up is taken from the vector/FTS index
     // specifically, not a BTree on the same column.
-    let (column, type_url_suffix, arm) = if !query.query_vector.is_empty() {
+    let mut arms: Vec<(String, &str, &str)> = Vec::new();
+    if !query.query_vector.is_empty() {
         let arrow_schema = ArrowSchema::from(dataset.schema());
         let column = match &query.column {
             Some(column) => column.clone(),
@@ -508,31 +551,43 @@ async fn arm_maintained_index_name(
                 default_vector_column(&arrow_schema, dim)?
             }
         };
-        (column, "VectorIndexDetails", "vector")
-    } else if let Some(fts) = &query.base.full_text_search {
-        match fts.columns().into_iter().next() {
-            Some(column) => (column, "InvertedIndexDetails", "full-text"),
-            None => return Ok(None),
-        }
-    } else {
-        return Ok(None);
-    };
-    let Some(field) = dataset.schema().field(&column) else {
-        return Ok(None);
-    };
+        arms.push((column, "VectorIndexDetails", "vector"));
+    }
+    if let Some(fts) = &query.base.full_text_search
+        && let Some(column) = fts.columns().into_iter().next()
+    {
+        arms.push((column, "InvertedIndexDetails", "full-text"));
+    }
+    if arms.is_empty() {
+        return Ok(Vec::new());
+    }
+
     let indices = dataset.load_indices().await?;
-    let segment_names: Vec<String> = indices
-        .iter()
-        .filter(|idx| {
-            idx.fields.contains(&field.id)
-                && idx
-                    .index_details
-                    .as_ref()
-                    .is_some_and(|d| d.type_url.ends_with(type_url_suffix))
-        })
-        .map(|idx| idx.name.clone())
-        .collect();
-    resolve_single_index(segment_names, &details.maintained_indexes, arm, &column)
+    let mut names = Vec::with_capacity(arms.len());
+    for (column, type_url_suffix, arm) in arms {
+        let Some(field) = dataset.schema().field(&column) else {
+            continue;
+        };
+        let segment_names: Vec<String> = indices
+            .iter()
+            .filter(|idx| {
+                idx.fields.contains(&field.id)
+                    && idx
+                        .index_details
+                        .as_ref()
+                        .is_some_and(|d| d.type_url.ends_with(type_url_suffix))
+            })
+            .map(|idx| idx.name.clone())
+            .collect();
+        if let Some(name) =
+            resolve_single_index(segment_names, &details.maintained_indexes, arm, &column)?
+        {
+            names.push(name);
+        }
+    }
+    names.sort();
+    names.dedup();
+    Ok(names)
 }
 
 /// Resolve the single logical index from the names of its matching physical
@@ -734,22 +789,117 @@ mod tests {
         };
 
         // Plain scan: drop every compacted generation (through 5).
-        assert_eq!(exclusion_watermarks(&details, None).get(&shard), Some(&5));
+        assert_eq!(
+            exclusion_watermarks(&details, &[], false).get(&shard),
+            Some(&5)
+        );
 
         // FTS arm with a lagging index: exclusion is capped at the index catch-up
         // (2), so SSTable generations 3..=5 are retained until the index covers
         // them — otherwise those documents would silently vanish from FTS results.
         assert_eq!(
-            exclusion_watermarks(&details, Some("fts_idx")).get(&shard),
+            exclusion_watermarks(&details, &["fts_idx".to_string()], false).get(&shard),
             Some(&2)
         );
 
         // A caught-up index — or one untracked in index_catchup — falls back to the
         // compaction watermark.
         assert_eq!(
-            exclusion_watermarks(&details, Some("caught_up_idx")).get(&shard),
+            exclusion_watermarks(&details, &["caught_up_idx".to_string()], false).get(&shard),
             Some(&5)
         );
+
+        // The same missing entry, once the table requires catch-up: absence now
+        // means "not known to hold these rows", so nothing may be excluded and
+        // every generation stays readable from its SSTable. This is the whole
+        // point of the protocol -- an indexed query against a table whose index
+        // has not caught up must not silently lose rows.
+        assert_eq!(
+            exclusion_watermarks(&details, &["untracked_idx".to_string()], true).get(&shard),
+            Some(&0)
+        );
+
+        // A tracked index is unaffected by the mode: the recorded position is
+        // information either way, and it still caps the exclusion.
+        assert_eq!(
+            exclusion_watermarks(&details, &["fts_idx".to_string()], true).get(&shard),
+            Some(&2)
+        );
+
+        // One missing entry is enough to hold everything back, even alongside an
+        // index that has caught up.
+        let mixed = vec!["fts_idx".to_string(), "untracked_idx".to_string()];
+        assert_eq!(
+            exclusion_watermarks(&details, &mixed, true).get(&shard),
+            Some(&0)
+        );
+    }
+
+    /// A hybrid search reads a vector and a full-text index, and either may lag.
+    /// Retaining to the lower of the two is what keeps both arms complete;
+    /// gating on one alone would drop SSTables the other has not indexed.
+    #[test]
+    fn exclusion_watermark_takes_the_minimum_across_every_index_used() {
+        let shard = Uuid::from_u128(1);
+        let details = MemWalIndexDetails {
+            compacted_sstables: vec![CompactedSsTable::new(shard, 9)],
+            index_catchup: vec![
+                IndexCatchupProgress::new(
+                    "vec_idx".to_string(),
+                    vec![CompactedSsTable::new(shard, 7)],
+                ),
+                IndexCatchupProgress::new(
+                    "fts_idx".to_string(),
+                    vec![CompactedSsTable::new(shard, 4)],
+                ),
+            ],
+            maintained_indexes: vec!["vec_idx".to_string(), "fts_idx".to_string()],
+            ..Default::default()
+        };
+
+        // Each index alone stops at its own catch-up.
+        assert_eq!(
+            exclusion_watermarks(&details, &["vec_idx".to_string()], false).get(&shard),
+            Some(&7)
+        );
+        assert_eq!(
+            exclusion_watermarks(&details, &["fts_idx".to_string()], false).get(&shard),
+            Some(&4)
+        );
+
+        // Used together, the lower one governs regardless of order.
+        let both = ["vec_idx".to_string(), "fts_idx".to_string()];
+        assert_eq!(
+            exclusion_watermarks(&details, &both, false).get(&shard),
+            Some(&4)
+        );
+        let reversed = ["fts_idx".to_string(), "vec_idx".to_string()];
+        assert_eq!(
+            exclusion_watermarks(&details, &reversed, false).get(&shard),
+            Some(&4)
+        );
+    }
+
+    /// An index with no catch-up entry contributes no cap today, so a lagging
+    /// sibling must still govern rather than being widened by the untracked one.
+    #[test]
+    fn an_untracked_index_does_not_widen_a_lagging_sibling() {
+        let shard = Uuid::from_u128(1);
+        let details = MemWalIndexDetails {
+            compacted_sstables: vec![CompactedSsTable::new(shard, 9)],
+            index_catchup: vec![IndexCatchupProgress::new(
+                "fts_idx".to_string(),
+                vec![CompactedSsTable::new(shard, 4)],
+            )],
+            maintained_indexes: vec!["fts_idx".to_string(), "untracked_idx".to_string()],
+            ..Default::default()
+        };
+
+        let both = ["fts_idx".to_string(), "untracked_idx".to_string()];
+        assert_eq!(
+            exclusion_watermarks(&details, &both, false).get(&shard),
+            Some(&4)
+        );
     }
 
     #[test]