mirror of
https://github.com/lancedb/lancedb.git
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Jack Ye
ddb318567a
## Summary - Complete the SQL reference: `ATTACH DATABASE`, the `CHANGES` clause, and `dedupe()`/`duplicate_pairs()` (verified against current sophon source; these were recently renamed from `vector_dedup`/`vector_duplicate_pairs`). Fix the blob-column default-projection claim and add the previously undocumented `blob_descriptor()`. - Enrich the gated Functions draft (still `.mintignore`'d, pre-release): chained Functions over blob outputs, GPU-produced blobs, Secrets, multi-input/output binding, `code=[module]` packaging. - Upgrade the materialized-view and computed-column auto-refresh drafts with precise, verified catch-up semantics, and add the missing `ALTER MATERIALIZED VIEW` / `CREATE ... WITH(...)` sections (also gated — the automatic-refresh scheduler is still dev/staging-only). - Thread one running example (video frames → GPU extract/caption → dedup → auto-refreshing materialized view) through Functions, materialized views, and the LeRobotDataset integration guide instead of a separate tutorial. - Rename "LanceDB OSS"/"OSS" to "LanceDB Embedded"/"Embedded" throughout (52 files); activate the existing availability-comparison mechanism on `basics/offerings.mdx` for a full feature-by-feature comparison table.
115 lines
3.7 KiB
Plaintext
115 lines
3.7 KiB
Plaintext
---
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title: "Function"
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sidebarTitle: "Function"
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description: "CREATE FUNCTION, SHOW FUNCTIONS, and DROP FUNCTION."
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icon: function
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keywords: ["create function", "drop function", "show functions", "sql", "udf"]
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---
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<Badge color="red">Enterprise</Badge> [SQL runs in LanceDB Enterprise.](/sql)
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## CREATE FUNCTION {#create}
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```sql
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CREATE FUNCTION f(x int64) RETURNS int64
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LANGUAGE python
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AS 'def f(x): return x * 2'
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WITH (pip = 'numpy==1.26.4', python_version = '3.11')
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```
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A function takes more than one parameter; each one binds a separate column
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or literal where the function is called:
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```sql
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CREATE FUNCTION ratio(numerator float64, denominator float64) RETURNS float64
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LANGUAGE python
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AS 'def ratio(numerator, denominator): return numerator / denominator'
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```
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Parameter and result types are Arrow type names, not SQL ones: `int64`,
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`float64`, `utf8`, `bool`, `date32`, and lists such as `list<float32>` or
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`fixed_size_list<float32, 768>`. `BIGINT` is refused. A parameter accepts nulls
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unless it is declared `NOT NULL`.
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The body is Python source. Its dependencies are declared with it and are part
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of the **immutable function version**. Changing one produces a new version
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rather than altering the registered one, so a column filled by an earlier
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version is unaffected.
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| Option | |
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| --- | --- |
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| `pip` | pip requirements for the worker environment |
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| `conda` | conda packages instead of pip |
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| `conda_channels` | channels in priority order; requires `conda` |
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| `python_version` | worker Python version; `3.12` when omitted, whatever Python you send the statement from |
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| `gpu` | `'true'` when every execution needs a GPU |
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**Errors and limits**
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| | |
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| --- | --- |
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| `LANGUAGE` other than `python` | refused |
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| `pip` and `conda` together | refused (pick one) |
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| `conda_channels` without `conda` | refused |
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| `gpu` set to anything but `'true'` | refused |
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| An empty body | refused |
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| Any other option | refused, and the message lists what is supported |
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<Note>
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**Enterprise job type:** `create_function`. Registration returns a job because
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the function is baked into an image before the version becomes usable.
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</Note>
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## Call it {#call}
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Once registered, a function is callable by name in any query, the same as a
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built-in scalar function:
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```sql
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SELECT id, f(x) AS doubled FROM my_table
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```
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This is also the fastest way to check a new registration before binding it to
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a column: call it over a few rows, or over literal arguments, before
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committing to [a computed column](/sql/ddl/table#computed-column) that fills
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from it.
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## SHOW FUNCTIONS {#show}
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```sql
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SHOW FUNCTIONS
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```
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Lists registered functions and their versions. Since a version is immutable
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and a column pins the version that fills it, this is how you find which
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versions are still in use before dropping one.
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## DROP FUNCTION {#drop}
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```sql
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DROP FUNCTION embed WITH (version = '1')
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DROP FUNCTION IF EXISTS embed WITH (version = '1')
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DROP FUNCTION embed WITH (version = '1', cascade = 'true')
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```
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`version` is required: a function is a set of immutable versions, and
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dropping is always of one specific version, never "the function" as a whole.
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<Warning>
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Without `cascade = 'true'`, dropping a version that a column still pins fails
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rather than breaking that column silently. Passing it drops the version and
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lets columns pinned to it stop refreshing. They keep their last-filled
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values, per [Guarantees](/basics/guarantees#jobs).
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</Warning>
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## What to read next {#next}
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<CardGroup cols={2}>
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<Card title="Function" icon="function" href="/management/function">
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Registering one from the SDK, and diagnosing environment mismatches.
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</Card>
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<Card title="Computed columns" icon="table-columns" href="/feature-engineering/add-computed-column">
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Filling a column with a function instead of an expression.
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</Card>
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</CardGroup>
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