feat: Add Vector Search support to MongoDBOnlineStore

[caseyclements]

What this PR does / why we need it:

Adds MongoDB Atlas Vector Search support to MongoDBOnlineStore, enabling similarity search over feature embeddings stored in MongoDB Atlas.

Changes:

• MongoDBOnlineStoreConfig: Extends VectorStoreConfig to inherit vector_enabled and similarity fields. Adds vector_index_wait_timeout for controlling how long to wait for newly created Atlas Search indexes to become queryable.

• MongoDBOnlineStore.update(): When vector_enabled=True, automatically creates Atlas vector search indexes for any FeatureView fields that have vector_index=True. Ensures the underlying collection exists before index creation (required by Atlas). Drops vector indexes for removed feature views.

• MongoDBOnlineStore.retrieve_online_documents_v2(): Implements similarity search using the $vectorSearch aggregation stage. Returns results as (event_ts, entity_key_proto, feature_dict) tuples with a synthetic distance field containing the vector search score. Coerces query vectors to native Python floats for BSON compatibility.

• MongoDBAtlasOnlineStoreCreator: Test infrastructure using MongoDBAtlasLocalContainer from testcontainers-python to spin up mongodb/mongodb-atlas-local:8.0.4 for integration testing.

• Integration tests (test_mongodb_vector_search.py): Covers index lifecycle (create on update(), drop on teardown()), write + retrieve round-trip with known embeddings, and top_k limiting.

Dependencies:

• Uses existing pymongo >= 4.13.0 Atlas Search index APIs (SearchIndexModel, create_search_index, list_search_indexes, drop_search_index). No change here.
• The integration tests require testcontainers.mongodb.MongoDBAtlasLocalContainer, which is, as of April 30th, available in testcontainers=4.15.0rc2. See testcontainers pull/873

Which issue(s) this PR fixes:

Closes MongoDB ticket INTPYTHON-921

Checks

• I've made sure the tests are passing.
• My commits are signed off (git commit -s)
• My PR title follows conventional commits format

Testing Strategy

• Unit tests
• Integration tests
• Manual tests
• Testing is not required for this change

Misc

The integration tests use the mongodb/mongodb-atlas-local:8.0.4 Docker image via testcontainers. A configurable INDEX_WAIT (default 5s) accounts for Atlas Search index eventual consistency after writes.

Verified that existing unit tests (676 passed) and MongoDB universal integration tests (75 passed) are unaffected by these changes.

[caseyclements]

Note: This will be rebased onto master. I mistakenly built from #6138

[ntkathole]

need to update requirements using make lock-python-dependencies-all, doesn't using stable release help ?

https://github.com/feast-dev/feast/blob/master/sdk/python/requirements/py3.12-ci-requirements.txt#L5740

[caseyclements]

1. Lockfiles regenerated via make lock-python-dependencies-all — included in latest push.
2. 4.15.0rc2 is the earliest release that includes MongoDBAtlasLocalContainer — there's no stable release with it yet. Changed to >=4.15.0rc2 so it will automatically pick up 4.15.0 stable once it ships.

[bisht2050]

@ntkathole - This is ready for your review/merge. TIA!

[ntkathole]

Looks good

[ntkathole]

@caseyclements Let's update the pixi lock file to fix failures and will merge

[caseyclements]

@caseyclements Let's update the pixi lock file to fix failures and will merge

I've updated in my environment - MacOS. CI is still failing. What needs to be done?

(feast) ~/src/feast (INTPYTHON-921)
$ pixi install -e registration-tests --locked
✔ The registration-tests environment has been installed.
(feast) ~/src/feast (INTPYTHON-921)
$ git ss
## INTPYTHON-921...origin/INTPYTHON-921
(feast) ~/src/feast (INTPYTHON-921)
$ pixi lock
✔ Lock-file was already up-to-date
(feast) ~/src/feast (INTPYTHON-921)

[ntkathole]

@caseyclements seems there are conflicts with master

[caseyclements]

@caseyclements seems there are conflicts with master

Oh. Of course. Thanks.

[caseyclements]

@ntkathole Are we good to merge? Failures appear to be unrelated.

● Here's the summary of all 4 failures:

Check	Failing tests	Ours?
unit-test-python (3.11, macos-14)	test_redis.py::test_online_write_batch_async_skip_dedup_single_pipeline — event loop error	No — Redis test
integration-test-python (3.11)	Snowflake materialization tests + Snowflake offline store tests	No — all Snowflake
integration-test-registration-ci	No module named 'MySQLdb'	No — MySQL driver missing
integration-test-registration-local	Same MySQL issue	No — MySQL driver missing

[ntkathole]

@caseyclements snowflake is expected but mysql failures are due to testcontainer version upgrade (testcontainers/testcontainers-python#739)

Change conftest.py to include dialect:

@pytest.fixture(scope="session")
def mysql_server():
    container = MySqlContainer("mysql:latest", dialect="pymysql")
    container.start()