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Jack Ye
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OSS docs now own the full usage content for features that only run against an Enterprise deployment, since the client interface itself lives here; Enterprise docs keep only the parts specific to its own behavior. Sophon's overlay for these five pages is dropped since the OSS versions are now the complete reference. SQL Reference is restructured to match an object-type SQL manual (DDL by object, then DML, then DQL, then Expressions) instead of the old flat, loosely-ordered page list, absorbing the SQL client-connection guide and FTS-via-SQL examples into it.
96 lines
3.0 KiB
Plaintext
96 lines
3.0 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 on a deployment.](/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 and **leaves filled rows alone**.
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That makes it idempotent, cheap to repeat as data arrives, and resumable after a
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failure -- re-running costs only the rows that did not complete.
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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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<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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## REFRESH MATERIALIZED VIEW {#refresh-materialized-view}
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```sql
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REFRESH MATERIALIZED VIEW <name> [WITH (<option> = <value>)]
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```
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```sql
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REFRESH MATERIALIZED VIEW chunks
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REFRESH MATERIALIZED VIEW chunks WITH (full = true)
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```
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By default a refresh is **incremental** -- it processes what the source has
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added since the last one. `full = true` recomputes every row, which is what you
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want after changing something the view's rows depend on.
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<Warning>
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`CASCADE` parses but is **not implemented**. A view built on another view is
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refreshed by refreshing each in dependency order yourself.
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</Warning>
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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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