## What
Renames the MemWAL surface in two passes, across Rust, Python,
TypeScript, and Java, including the wire format.
### 1. MemWAL APIs drop "LSM"
The write path these APIs drive is Lance's MemWAL; "LSM" described its
shape rather than naming it. Turning it on and off now reads as enabling
a feature rather than installing a spec.
| Before | After |
|---|---|
| `set_lsm_write_spec` | `enable_memwal` |
| `unset_lsm_write_spec` | `disable_memwal` |
| `get_lsm_write_spec` | `get_memwal_spec` |
| `flush_lsm` / `compact_lsm` / `checkpoint_lsm` | `flush_memwal` /
`compact_memwal` / `checkpoint_memwal` |
| `get_lsm_stats` | `get_memwal_stats` |
| `close_lsm_writers` | `close_memwal_writers` |
| `use_lsm` (query, merge insert) | `use_memwal` |
| `LsmWriteSpec` / `LsmStats` | `MemWalWriteSpec` / `MemWalStats` |
| Java `LanceDbTableLsm` | `LanceDbTableMemWal` |
TypeScript and Java use camelCase (`enableMemWal`, `getMemWalStats`,
...); the napi methods set `js_name` so the generated names keep the
`MemWal` casing. flush/compact/checkpoint keep a `_memwal` suffix so
`compact_memwal` is not confused with `compact_files` / `optimize`,
which compact the base table.
Internal names (`LsmMode`, `LsmScanner`, the `merge::lsm` / `query::lsm`
modules) are unchanged.
### 2. Stats use SSTable and table shard
Aligns the stats surface with the MemWAL naming settled upstream in
lance-format/lance#7943 and #7957, where the persisted unit became an
**SSTable**.
**Generation → SSTable.** A `GenerationStats` describes one flushed
MemTable, which is an SSTable. The generation *number* is kept — an
SSTable is identified by its generation — so only the noun moved.
**Bucket → table shard.** Each entry is one MemWAL shard. "Bucket" names
only the hash sharding *transform*, so it was already wrong for
`identity` and `year` sharding, which produce shards and no buckets at
all.
| Before | After |
|---|---|
| `GenerationStats` | `SsTableStats` |
| `BucketStats` | `TableShardStats` |
| `stats.buckets` | `stats.table_shards` |
| `BucketStats.generations` | `TableShardStats.sstables` |
| `include_generation_rows` | `include_sstable_rows` |
| `newest_generation` | `newest_sstable_generation` |
| `outstanding_generations` | `outstanding_sstables` |
Docs and comments follow suit: "seal" → "freeze", "L0" / "flushed
generations" → SSTables, "bucket" (meaning a shard) → table shard.
`MemWalWriteSpec::bucket`, `num_buckets`, and the `"Sealed"` shard
status value are **unchanged** — those name the sharding transform or a
server value, not the shard.
## Compatibility
Breaking, for an experimental API. The wire format changes with the
SDKs, so this must roll out together with the matching server change:
- Routes: `/set_lsm_write_spec/` → `/enable_memwal/`,
`/unset_lsm_write_spec/` → `/disable_memwal/`, `/get_lsm_write_spec/` →
`/get_memwal_spec/`, `/flush_lsm/` → `/flush_memwal/`, `/compact_lsm/` →
`/compact_memwal/`, `/get_lsm_stats/` → `/get_memwal_stats/`
- Response keys: `lsm_write_spec` → `memwal_spec`, `lsm_stats` →
`memwal_stats`, `buckets` → `table_shards`, `generations` → `sstables`
- Request fields: `include_generation_rows` → `include_sstable_rows`;
`use_lsm` → `use_memwal` on query and merge-insert bodies
## Validation
- Rust: `cargo test --features remote -p lancedb --lib --tests` — 1467
lib tests and all integration test targets pass; `cargo clippy` clean
- Python: rebuilt the extension; `test_remote_db`, `test_memwal_spec`,
`test_merge_insert_lsm`, `test_query`, `test_permutation`, `test_table`
— 655 passed; `ruff format` / `ruff check` clean
- TypeScript: `pnpm build`; `table`, `merge`, `query` tests — 593
passed; `biome check` clean; `docs/src/js` regenerated with `npm run
docs`
- Java: `mvn test` — 37 passed (Spotless applied with JDK 11; the pinned
google-java-format does not run on JDK 21)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
## Summary
The Java SDK pinned `jackson-databind` 2.17.1, and `jackson-core` and
the other Jackson modules came in transitively via `arrow-vector` and
`lance-namespace-apache-client` at 2.16.x–2.17.x, all affected by known
CVEs.
This imports `jackson-bom` 2.18.11 in the parent POM, and declares
`jackson-core`, `jackson-annotations`, `jackson-datatype-jsr310`, and
`jackson-jaxrs-json-provider` as direct (BOM-managed) dependencies of
`lancedb-core`. The direct declarations are needed because the parent's
dependency management doesn't apply to a consumer's transitive
resolution; without them, Maven's nearest-wins mediation still hands
downstream apps the older versions from `arrow-vector`.
## Evidence
`mvn dependency:list` in a separate consumer project depending only on
`lancedb-core`:
| Artifact | Before | After |
|---|---|---|
| jackson-core | 2.16.0 | 2.18.11 |
| jackson-annotations | 2.16.0 | 2.18.11 |
| jackson-databind | 2.17.1 | 2.18.11 |
| jackson-datatype-jsr310 | 2.16.0 | 2.18.11 |
| jackson-jaxrs-base / json-provider | 2.17.1 | 2.18.11 |
| jackson-module-jaxb-annotations | 2.17.1 | 2.18.11 |
## Merge Risk
**Door:** Two-way. Dependency versions only, and they stay within
Jackson 2.x.
**Blast Radius:** `java` dependencies. Downstream users of
`lancedb-core` now get Jackson 2.18.11 transitively.
Fixes OSS-2360, OSS-2337
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
`maintained_indexes` on a MemWAL table has three values: a named list,
`[]` for none, and `null` for every index the table has, including ones
created later. This PR makes every client read all three back as they
were set.
- **Rust remote client** (also used by the Python and Node SDKs) reads
`null` as `None`.
- **Java client** reads `null` as `null`, not as an empty list.
- **Docs** for the setter, the field and the getter describe the three
values the same way in Rust, Python, Node and Java. The generated JS
docs are regenerated to match.
## Testing
- `rust/lancedb`: 73 LSM tests pass, including one case per value. With
the decoder typed as a list, the `null` case fails.
- Java: two cases for `null` and `[]` on the read path, run by the Java
CI job.
- `cargo fmt`, `cargo clippy -D warnings` and `ruff format` are clean.
Dan RammerandClaude Opus 5
Lance Release
Will JonesandClaude Opus 5.5
XY Zhan