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Brendan Clement
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This PR is part of the documentation revamp. Once the full set of PRs is merged, we’ll publish the combined site to staging for review before updating docs.lancedb.com. The curation, SQL and operations pages contain outdated claims and examples that do not reliably work as written. This corrects those pages against the reviewed SDK and local server evidence, including prepared statements, background jobs, cleanup and monitoring. Integration guides are grouped with their examples in #4533. Function and Secret-object documentation stays unpublished until its release. The two Function pages are listed in `.mintignore` and left out of the navigation, and the sections about them on other pages are MDX comments. Stacked on #4533. Each MDX file has one PR owner. Rebase onto main after #4533 is squash-merged. Local assembly, Mint validation and link checks pass, and the assembled site shows no Function or Secret-object content. A local release rehearsal that uncomments the drafts and restores the navigation also passes. Hold publication until this PR and lancedb/sophon#8688 are on `main`.
101 lines
3.1 KiB
Plaintext
101 lines
3.1 KiB
Plaintext
---
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title: "REFRESH"
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sidebarTitle: "REFRESH"
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description: "Filling computed columns and bringing materialized views up to date."
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icon: arrows-rotate
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keywords: ["refresh column", "refresh materialized view", "backfill", "cascade"]
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---
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<Badge color="red">Enterprise</Badge> [SQL runs in LanceDB Enterprise.](/sql)
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LanceDB extensions with no DataFusion equivalent. They are what makes
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[feature engineering](/feature-engineering) reachable from SQL: a column
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declared by [DDL](/sql/ddl/table#computed-column) starts empty, and a refresh fills it.
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## REFRESH COLUMN {#refresh-column}
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```sql
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REFRESH COLUMN <column> ON [TABLE] <table>
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[WHERE <predicate>]
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[WITH (<option> = <value> [, ...])]
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```
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```sql
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REFRESH COLUMN doubled ON my_table
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REFRESH COLUMN embedding ON documents WHERE created_at > '2026-01-01'
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```
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A refresh gives values to rows that lack them, recomputes rows whose inputs
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changed, and **leaves other filled rows alone**. That makes it idempotent, cheap
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to repeat as data arrives, and safe to re-run after a failure -- though a re-run
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can recompute values the failed run had already written.
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`WHERE` scopes the refresh, which is how you fill a slice and check it before
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committing to the whole table.
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### Options {#refresh-column-options}
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| Option | Meaning |
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| --- | --- |
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| `num_workers` | how many workers to use |
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| `cpu_millis` | CPU budget per worker |
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| `memory_bytes` | memory budget per worker |
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| `gpu_count` | GPUs per worker |
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| `batch_size` | rows a worker takes at a time |
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| `error_policy` | `'skip'` continues past failing rows instead of failing the job |
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```sql
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REFRESH COLUMN embedding ON documents
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WITH (cpu_millis = 8000, memory_bytes = 17179869184, gpu_count = 2)
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```
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`num_workers` sets a count; the budget options size each worker. They are
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alternatives rather than a pair.
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{/*
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Draft for the Functions release.
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<Note>
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`error_policy` and `num_workers` are refused for a column filled by a registered
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[function](/management/function) with its own resource budget -- use the CPU,
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memory and GPU options there.
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</Note>
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*/}
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## REFRESH MATERIALIZED VIEW {#refresh-materialized-view}
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```sql
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REFRESH MATERIALIZED VIEW <name>
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```
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```sql
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REFRESH MATERIALIZED VIEW chunks
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```
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A refresh updates the view's stored result. Refresh views in dependency order,
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starting with their source views.
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<Note>
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Some older server versions accepted `WITH (full = true)` and `CASCADE`.
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Those options are not accepted by the SQL implementation described here.
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Use the basic statement above; do not assume that the options accepted by a
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local SDK's `refresh()` method are also SQL options.
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</Note>
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## Watching a refresh {#watching}
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Both statements submit work that outlives the call. Track it with
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[`SHOW JOBS`](/sql/ddl/job#show), and diagnose failures with
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[`SHOW ERRORS`](/sql/ddl/job#errors).
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## See also {#see-also}
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<CardGroup cols={2}>
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<Card title="Refresh a column" icon="arrows-rotate" href="/feature-engineering/refresh-column">
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The same operation from the SDKs, and what a refresh guarantees.
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</Card>
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<Card title="Table" icon="table" href="/sql/ddl/table#alter">
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Declaring the columns this fills.
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</Card>
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</CardGroup>
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