> ## Documentation Index
> Fetch the complete documentation index at: https://planetscale.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Postgres extensions

> Manage Postgres extensions for Neki configuration profiles.

Postgres extensions add data types, functions, operators, background workers,
and other capabilities to Postgres. Extensions that do not require a
profile-level toggle install in a logical database with `CREATE EXTENSION`.

## Extension availability

Extensions marked **Always enabled** are part of Neki's managed configuration
and cannot be toggled. Other extensions can use either of these workflows:

* A checkbox enables server configuration that the extension needs, such as a
  preload setting. Changing it creates a configuration-profile change.
* An extension without a checkbox does not require a profile-level toggle. You
  install it in a logical database with `CREATE EXTENSION` when it is available.

Enabling an extension for a configuration profile and installing its database
objects are separate operations. A profile-level change applies to the
Postgres instances in shards assigned to that profile. `CREATE EXTENSION`
installs objects in the logical database to which you are connected.

## Enable an extension for a profile

You must have permission to update the database, and the branch must be ready.

<Steps>
  <Step>From the PlanetScale dashboard, select your Neki database and branch.</Step>
  <Step>Open **Clusters** and select the configuration profile used by the target shards.</Step>
  <Step>Select the **Extensions** tab.</Step>
  <Step>Enable the extension. If the extension exposes parameters, review and update them.</Step>
  <Step>Select **Apply now** for any parameter changes.</Step>
  <Step>Open **Changes** and wait for the configuration change to finish before using the extension.</Step>
</Steps>

<Warning>
  A configuration-profile change affects every shard assigned to that profile.
  Confirm the assigned shards before changing an extension or its parameters.
</Warning>

Some profile changes can restart Postgres processes or roll through the
instances in the profile. Use the change status to follow the rollout and avoid
making dependent application changes before it completes.

The available extension list for a profile is also available from
`pscale branch config-profile extensions`. Enable or disable a catalog
extension that the profile marks as enablable with
`pscale branch config-profile extensions enable` or
`pscale branch config-profile extensions disable`.

## Install an extension in a logical database

After any required profile change has completed, connect to the target logical
database with its default role. When the extension's instructions require
database installation, run:

```sql theme={null}
CREATE EXTENSION IF NOT EXISTS extension_name;
```

Replace `extension_name` with the extension you want to install. Repeat
the command for each logical database that needs the extension.

To see extensions that are installed in the current logical database:

```sql theme={null}
SELECT name, default_version, installed_version, comment
FROM pg_available_extensions
WHERE installed_version IS NOT NULL
ORDER BY name;
```

To see every extension that Postgres reports as available to the current
logical database:

```sql theme={null}
SELECT name, default_version, installed_version, comment
FROM pg_available_extensions
ORDER BY name;
```

<Warning>
  During Platform Preview, do not use `ALTER EXTENSION ... ADD` to attach a
  user-created table, type, function, sequence, view, or other object to an
  extension. A shard created or rebuilt later may not recreate that object.
  Contact PlanetScale Support before using extension-membership DDL.
</Warning>

## Supported extensions

### Always enabled

These extensions are part of Neki's managed configuration and cannot be
disabled.

| Extension         | Version | Purpose                                                                                       |
| ----------------- | ------- | --------------------------------------------------------------------------------------------- |
| `neki_xxhash`     | 0.4     | Hash functions used by Neki distribution                                                      |
| `pg_pscale_utils` | —       | Handles privileged actions without granting superuser access                                  |
| `pgextwlist`      | —       | Controls which extensions can be installed                                                    |
| `pginsights`      | —       | Collects per-query execution statistics for [Query Insights](/docs/neki/monitoring/query-insights) |
| `plpgsql`         | 1.0     | Built-in PL/pgSQL procedural language                                                         |

### Customer-configurable

| Extension                        | Version | Profile toggle | Database install                 | Notes                                                                                                      |
| -------------------------------- | ------- | -------------- | -------------------------------- | ---------------------------------------------------------------------------------------------------------- |
| `citext`                         | 1.8     | —              | `CREATE EXTENSION citext`        |                                                                                                            |
| `cube`                           | 1.5     | —              | `CREATE EXTENSION cube`          |                                                                                                            |
| `fuzzystrmatch`                  | 1.2     | —              | `CREATE EXTENSION fuzzystrmatch` |                                                                                                            |
| `hstore`                         | 1.8     | —              | `CREATE EXTENSION hstore`        |                                                                                                            |
| `intarray`                       | 1.5     | —              | `CREATE EXTENSION intarray`      |                                                                                                            |
| `ltree`                          | 1.3     | —              | `CREATE EXTENSION ltree`         |                                                                                                            |
| `pg_trgm`                        | 1.6     | —              | `CREATE EXTENSION pg_trgm`       |                                                                                                            |
| `pgcrypto`                       | 1.4     | —              | `CREATE EXTENSION pgcrypto`      |                                                                                                            |
| `unaccent`                       | 1.1     | —              | `CREATE EXTENSION unaccent`      |                                                                                                            |
| `uuid-ossp`                      | 1.1     | —              | `CREATE EXTENSION "uuid-ossp"`   |                                                                                                            |
| [`vector`](#pgvector) (pgvector) | 0.8.6   | Enable         | `CREATE EXTENSION vector`        | Usable on unsharded and sharded Neki with [query-shape limits](#pgvector)                                  |
| [`vectorscale`](#vectorscale)    | 0.9.0   | Enable         | `CREATE EXTENSION vectorscale`   | Requires `vector`. Exposes DiskANN query parameters. Inherits the [pgvector query-shape limits](#pgvector) |

## Extension-specific caveats

Neki can use an extension without implementing every function, cast, or
cross-shard query shape that Postgres accepts on a single node. Prefer the
working forms below. A rejected shape often returns `NK013` for an
unimplemented input, receive, or user-defined function.

### pgvector

Install [pgvector](https://github.com/pgvector/pgvector) after you enable it
on the configuration profile:

```sql theme={null}
CREATE EXTENSION IF NOT EXISTS vector;
```

Nearest-neighbor search works for `vector`, `halfvec`, `sparsevec`, and binary
vectors, including HNSW and IVFFlat indexes. Tenant-scoped and shard-targeted
searches work. Cross-shard search works when the distance expression is
projected once and the global sort references that projected value:

```sql theme={null}
SELECT tenant_id, item_id, embedding <-> '[1,0,0]'::vector AS distance
FROM public.vector_items
ORDER BY distance
LIMIT 20;
```

The same alias-based shape works for cosine (`<=>`), inner product (`<#>`), L1,
halfvec, sparsevec, Hamming, and Jaccard distance.

Repeating the distance expression in `ORDER BY` fails on sharded Neki:

```sql theme={null}
-- Rejected: NK013 receive function vector_recv is not implemented
SELECT tenant_id, item_id, embedding <-> '[1,0,0]'::vector AS distance
FROM public.vector_items
ORDER BY embedding <-> '[1,0,0]'::vector
LIMIT 20;
```

Other current limits:

* A prepared parameter declared as `vector` fails with `NK013` because
  `vector_in` is not implemented. Declare the parameter as `text` and cast
  `$1::vector` inside the query.
* `ARRAY[...]::vector` and `ARRAY[...]::vector(8)` are rejected. Use a vector
  literal such as `'[1,0,0]'::vector`.
* `l2_norm(embedding)` is rejected as ambiguous even when the column type is
  `vector`.
* Global `avg(vector)` and `sum(vector)` fail on sharded tables with
  `vector_recv`. Tenant-scoped and direct-shard aggregates work.
* Routed `INSERT ... SELECT` of vector values can hit the same `vector_recv`
  limit. Insert vector literals, or load rows with a query that stays on one
  shard.
* IVFFlat recall is poor at the default `ivfflat.probes=1`. Raise `probes`
  when you need higher recall. HNSW recall depends on `hnsw.ef_search`.

### vectorscale

[vectorscale](https://github.com/timescale/pgvectorscale) adds
StreamingDiskANN indexes on top of pgvector. Install `vector` first, then:

```sql theme={null}
CREATE EXTENSION IF NOT EXISTS vectorscale;
```

Tenant-routed and scatter searches that use a StreamingDiskANN index work when
they follow the [pgvector `ORDER BY distance` shape](#pgvector). The pgvector
parameter-binding, literal-cast, and `vector_recv` limits also apply, including
routed `INSERT ... SELECT` of vector values.

After `vectorscale` is enabled, the **Extensions** tab exposes these DiskANN query parameters:

| Parameter                        | Dashboard default | Description                                               |
| -------------------------------- | ----------------- | --------------------------------------------------------- |
| `diskann.query_search_list_size` | `100`             | The size of the search list used in queries.              |
| `diskann.query_rescore`          | `50`              | The number of elements rescored (`0` disables rescoring). |

## Change extension parameters

Parameters associated with an extension appear beneath it after the extension
is enabled. Their valid values, defaults, and restart requirements are shown in
the dashboard. Updating them creates the same kind of configuration-profile
change as other [configuration parameters](/docs/neki/cluster-configuration/parameters).

## Disable or remove an extension

Disabling a profile-level extension setting does not run `DROP EXTENSION` and
does not remove database objects from logical databases. Before disabling it,
remove or migrate any database objects and application features that depend on
it according to that extension's instructions.

`DROP EXTENSION` is a separate Postgres operation and can remove dependent
objects. Review the objects that depend on an extension before running it.

## Need help?

Get help from [the PlanetScale Support team](https://planetscale.com/contact?initial=support), or join our [Discord community](https://pscale.link/community) to see how others are using PlanetScale.