# PostgreSQL (contrib)

## Description

The PostgreSQL online store provides support for materializing feature values into a PostgreSQL database for serving online features.

* Only the latest feature values are persisted
* sslmode, sslkey\_path, sslcert\_path, and sslrootcert\_path are optional

## Getting started

In order to use this online store, you'll need to run `pip install 'feast[postgres]'`. You can get started by then running `feast init -t postgres`.

## Example

{% code title="feature\_store.yaml" %}

```yaml
project: my_feature_repo
registry: data/registry.db
provider: local
online_store:
    type: postgres
    host: DB_HOST
    port: DB_PORT
    database: DB_NAME
    db_schema: DB_SCHEMA
    user: DB_USERNAME
    password: DB_PASSWORD
    sslmode: verify-ca
    sslkey_path: /path/to/client-key.pem
    sslcert_path: /path/to/client-cert.pem
    sslrootcert_path: /path/to/server-ca.pem
    pgvector_enabled: false
    vector_len: 512
```

{% endcode %}

The full set of configuration options is available in [PostgreSQLOnlineStoreConfig](https://rtd.feast.dev/en/master/#feast.infra.online_stores.contrib.postgres.PostgreSQLOnlineStoreConfig).

## Functionality Matrix

The set of functionality supported by online stores is described in detail [here](https://docs.feast.dev/v0.37-branch/reference/overview#functionality). Below is a matrix indicating which functionality is supported by the Postgres online store.

|                                                           | Postgres |
| --------------------------------------------------------- | -------- |
| write feature values to the online store                  | yes      |
| read feature values from the online store                 | yes      |
| update infrastructure (e.g. tables) in the online store   | yes      |
| teardown infrastructure (e.g. tables) in the online store | yes      |
| generate a plan of infrastructure changes                 | no       |
| support for on-demand transforms                          | yes      |
| readable by Python SDK                                    | yes      |
| readable by Java                                          | no       |
| readable by Go                                            | no       |
| support for entityless feature views                      | yes      |
| support for concurrent writing to the same key            | no       |
| support for ttl (time to live) at retrieval               | no       |
| support for deleting expired data                         | no       |
| collocated by feature view                                | yes      |
| collocated by feature service                             | no       |
| collocated by entity key                                  | no       |

To compare this set of functionality against other online stores, please see the full [functionality matrix](https://docs.feast.dev/v0.37-branch/reference/overview#functionality-matrix).

## PGVector

The Postgres online store supports the use of [PGVector](https://pgvector.dev/) for storing feature values. To enable PGVector, set `pgvector_enabled: true` in the online store configuration. The `vector_len` parameter can be used to specify the length of the vector. The default value is 512.

Then you can use `retrieve_online_documents` to retrieve the top k closest vectors to a query vector.

{% code title="python" %}

```python
from feast import FeatureStore
from feast.infra.online_stores.postgres import retrieve_online_documents

feature_store = FeatureStore(repo_path=".")

query_vector = [0.1, 0.2, 0.3, 0.4, 0.5]
top_k = 5

feature_values = retrieve_online_documents(
    feature_store=feature_store,
    feature_view_name="document_fv:embedding_float",
    query_vector=query_vector,
    top_k=top_k,
)
```

{% endcode %}