feat: Add sqlite offline store

docs/reference/offline-stores/sqlite.md

@@ -0,0 +1,58 @@
+# SQLite offline store
+
+## Description
+
+The SQLite offline store provides support for reading and writing feature data using SQLite databases. It's a lightweight, file-based offline store option that's ideal for local development, testing, and small-scale deployments.
+
+* Entity dataframes can be provided as a Pandas dataframe or as a SQL query.
+* The SQLite offline store supports all core Feast functionality including point-in-time joins.
+
+## Getting started
+In order to use this offline store, you'll need to run `pip install 'feast[sqlite]'`.
+
+## Example
+
+{% code title="feature_store.yaml" %}
+```yaml
+project: my_project
+registry: data/registry.db
+provider: local
+offline_store:
+    type: sqlite
+    path: data/offline.db
+online_store:
+    path: data/online_store.db
+```
+{% endcode %}
+
+## Functionality Matrix
+
+The set of functionality supported by offline stores is described in detail [here](overview.md#functionality).
+Below is a matrix indicating which functionality is supported by the SQLite offline store.
+
+|                                                                    | SQLite |
+| :----------------------------------------------------------------- | :----- |
+| `get_historical_features` (point-in-time correct join)             | yes    |
+| `pull_latest_from_table_or_query` (retrieve latest feature values) | yes    |
+| `pull_all_from_table_or_query` (retrieve a saved dataset)          | yes    |
+| `offline_write_batch` (persist dataframes to offline store)        | yes    |
+| `write_logged_features` (persist logged features to offline store) | yes    |
+
+Below is a matrix indicating which functionality is supported by `SqliteRetrievalJob`.
+
+|                                                       | SQLite |
+| ----------------------------------------------------- | ------ |
+| export to dataframe                                   | yes    |
+| export to arrow table                                 | yes    |
+| export to arrow batches                               | no     |
+| export to SQL                                         | no     |
+| export to data lake (S3, GCS, etc.)                   | no     |
+| export to data warehouse                              | no     |
+| export as Spark dataframe                             | no     |
+| local execution of Python-based on-demand transforms  | yes    |
+| remote execution of Python-based on-demand transforms | no     |
+| persist results in the offline store                  | yes    |
+| preview the query plan before execution               | no     |
+| read partitioned data                                 | no     |
+
+To compare this set of functionality against other offline stores, please see the full [functionality matrix](overview.md#functionality-matrix).

infra/feast-operator/api/v1alpha1/featurestore_types.go

@@ -309,6 +309,7 @@ var ValidOfflineStoreFilePersistenceTypes = []string{
 	"dask",
 	"duckdb",
 	"file",
+	"sqlite",
 }
 
 // OfflineStoreDBStorePersistence configures the DB store persistence for the offline store service