lancedb/docs/web/sql/ddl/function.mdx

---
title: "Function"
sidebarTitle: "Function"
description: "Create, describe, alter, list, and drop registered functions with SQL."
icon: function
keywords: ["create function", "drop function", "show functions", "sql", "udf"]
---

<Badge color="red">Enterprise</Badge> [SQL runs in LanceDB Enterprise.](/sql)

## CREATE FUNCTION {#create}

```sql
CREATE FUNCTION f(x int64) RETURNS int64
LANGUAGE python
AS 'def f(x): return x * 2'
WITH (pip = 'numpy==1.26.4', python_version = '3.11')
```

A function takes more than one parameter; each one binds a separate column
or literal where the function is called:

```sql
CREATE FUNCTION ratio(numerator float64, denominator float64) RETURNS float64
LANGUAGE python
AS 'def ratio(numerator, denominator): return numerator / denominator'
```

Parameter and result types are Arrow type names, not SQL ones: `int64`,
`float64`, `utf8`, `bool`, `date32`, and lists such as `list<float32>` or
`fixed_size_list<float32, 768>`. `BIGINT` is refused. A parameter accepts nulls
unless it is declared `NOT NULL`.

The body is Python source. Its dependencies are declared with it and are part
of the **immutable function version**. Changing one produces a new version
rather than altering the registered one, so a column filled by an earlier
version is unaffected.

| Option | |
| --- | --- |
| `pip` | pip requirements for the worker environment |
| `conda` | conda packages instead of pip |
| `conda_channels` | channels in priority order; requires `conda` |
| `python_version` | worker Python version; `3.12` when omitted, whatever Python you send the statement from |
| `gpu` | `'true'` when every execution needs a GPU |

**Errors and limits**

| | |
| --- | --- |
| `LANGUAGE` other than `python` | refused |
| `pip` and `conda` together | refused (pick one) |
| `conda_channels` without `conda` | refused |
| `gpu` set to anything but `'true'` | refused |
| An empty body | refused |
| Any other option | refused, and the message lists what is supported |

<Note>
**Enterprise job type:** `create_function`. Registration returns a job because
the function is baked into an image before the version becomes usable.
</Note>

## Artifact registration {#artifact}

`CREATE FUNCTION name FROM '<registration JSON>'` accepts the artifact,
signature, runtime, optional secret bindings, and result stability produced by
the SDK's registration request. Omit its `name` property because the SQL
identifier supplies it. Escape apostrophes in the JSON as doubled apostrophes.

By default, the command waits for its internal image-build job to publish the
version, then returns one UTF-8 `definition` column containing FunctionVersion
JSON. `WITH (wait = false)` instead returns the existing image-build registry
job ID in `job_id`, with `operation` and `status` columns. The SDK's ordinary
registration handle has type `query` and uses the SQL query UUID as its single
`id`; the internal image-build job has type `create_function`.

## DESCRIBE and ALTER FUNCTION {#describe-alter}

```sql
DESCRIBE FUNCTION embed WITH (version = '1', include_source = true)
```

DESCRIBE returns one `definition` JSON column for the exact version.
`include_source` defaults to false; source-inclusive reads report an omission
when the stored artifact exceeds the inline source limit.

`ALTER FUNCTION name FROM '<pinned update JSON>'` accepts a `reference` with
name, namespace, object ID, location, version, and manifest digest, plus optional
`metadata` and `disabled` updates. The command checks that reference before
appending a revision and returns the resulting `definition` JSON.

## Call it {#call}

Once registered, a function is callable by name in any query, the same as a
built-in scalar function:

```sql
SELECT id, f(x) AS doubled FROM my_table
```

This is also the fastest way to check a new registration before binding it to
a column: call it over a few rows, or over literal arguments, before
committing to [a computed column](/sql/ddl/table#computed-column) that fills
from it.

## SHOW FUNCTIONS {#show}

```sql
SHOW FUNCTIONS
SHOW FUNCTIONS IN "analytics" WITH (name = 'embed', limit = 100)
SHOW FUNCTIONS WITH (after_name = 'embed', after_version = '1', limit = 100)
```

Rows are ordered lexicographically by name and version. `after_name` and
`after_version` must be supplied together for keyset pagination. `limit` bounds
the response; `include_definition = false` omits the optional definition JSON.

## DROP FUNCTION {#drop}

```sql
DROP FUNCTION embed WITH (version = '1')
DROP FUNCTION IF EXISTS embed WITH (version = '1')
```

`version` must identify an existing revision. DROP releases the function name
and its object binding; physical cleanup continues separately. The result
reports `dropped` or `not_found`. `IF EXISTS` allows a missing name.

All function object commands retain shared results even when general query-result
copying is disabled, so asynchronous polling can resume on another query node.

## What to read next {#next}

<CardGroup cols={2}>
  <Card title="Function" icon="function" href="/management/function">
    Registering one from the SDK, and diagnosing environment mismatches.
  </Card>
  <Card title="Computed columns" icon="table-columns" href="/feature-engineering/add-computed-column">
    Filling a column with a function instead of an expression.
  </Card>
</CardGroup>