refactor(api): use sessionmaker in pgvecto_rs VDB service

[carlos4s]

Summary

• Replace with Session(self._client) + session.commit() with
  sessionmaker(bind=self._client).begin() in pgvecto_rs VDB service (6 blocks)
• Read-only session blocks left unchanged
• Updated test mocks to patch both Session and sessionmaker

Part of #24245

Test plan

• ruff check passes
• 11 pgvecto_rs tests pass

[github-actions]

Pyrefly Diff

base → PR

--- /tmp/pyrefly_base.txt	2026-04-09 05:39:42.968336153 +0000
+++ /tmp/pyrefly_pr.txt	2026-04-09 05:39:34.492282664 +0000
@@ -163,7 +163,7 @@
 ERROR Function declared to return `bool`, but one or more paths are missing an explicit `return` [bad-return]
    --> core/rag/datasource/vdb/oracle/oraclevector.py:191:39
 ERROR No matching overload found for function `sqlalchemy.sql.sqltypes.UUID.__init__` called with arguments: (as_uuid=Literal[True]) [no-matching-overload]
-  --> core/rag/datasource/vdb/pgvecto_rs/pgvecto_rs.py:67:32
+  --> core/rag/datasource/vdb/pgvecto_rs/pgvecto_rs.py:66:32
 ERROR Argument `str | None` is not assignable to parameter `database_name` with type `str` in function `tcvectordb.rpc.client.stub.RPCVectorDBClient.describe_collection` [bad-argument-type]
   --> core/rag/datasource/vdb/tencent/tencent_vector.py:82:35
 ERROR Object of class `FilterIndex` has no attribute `dimension`

[Copilot]

Pull request overview

Refactors the PGVectoRS vector DB service’s write transactions to use SQLAlchemy’s sessionmaker(...).begin() context manager, aligning writes with transactional scope semantics and removing explicit commit() calls. This is part of the broader effort in #24245.

Changes:

• Replaced multiple with Session(engine) + commit() write blocks with with sessionmaker(bind=engine).begin() in the PGVectoRS service.
• Kept read-only session usage unchanged.
• Updated unit tests to patch both Session and sessionmaker to match the new transaction pattern.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
api/core/rag/datasource/vdb/pgvecto_rs/pgvecto_rs.py	Uses sessionmaker(...).begin() for write transactions; removes explicit commits.
api/tests/unit_tests/core/rag/datasource/vdb/pgvecto_rs/test_pgvecto_rs.py	Adds test helpers/mocks for sessionmaker().begin() and patches both session entrypoints.

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[Copilot]

sessionmaker(bind=self._client) is instantiated inline in multiple methods. Consider creating a single session factory in __init__ (e.g., self._sessionmaker = sessionmaker(bind=self._client)) and then using with self._sessionmaker.begin() as session: everywhere to reduce duplication and make future configuration/testing simpler.

[carlos4s]

@asukaminato0721 Thank you very much.