SNOW-1878372: Fix analyzer access across threads

[sfc-gh-aalam]

1. Which Jira issue is this PR addressing? Make sure that there is an accompanying issue to your PR.

   Fixes SNOW-1878372

2. Fill out the following pre-review checklist:

   • I am adding a new automated test(s) to verify correctness of my new code
     • If this test skips Local Testing mode, I'm requesting review from @snowflakedb/local-testing
   • I am adding new logging messages
   • I am adding a new telemetry message
   • I am adding new credentials
   • I am adding a new dependency
   • If this is a new feature/behavior, I'm adding the Local Testing parity changes.
   • I acknowledge that I have ensured my changes to be thread-safe. Follow the link for more information: Thread-safe Developer Guidelines

3. Please describe how your code solves the related issue.

   In this change, we make the following changes to Selectable:

   • the analyzer object is accessed via a thread so that each selectable uses the analyzer created for the dedicated thread.
   • the analyzer can be set to a different analyzer only during optimization stage when _is_valid_for_replacement=True.

We also update Analyzer to initialize alias_maps_to_use with an empty dict {} instead of None. In single threaded-case, resolve would initialize alias_maps_to_use to {} and then use it for analyze but in multithreaded-case, it is possible for one thread to call resolve and a different thread to call analyze.

[sfc-gh-jrose]

What does adding mock_session do for these tests?

[sfc-gh-aalam]

that's a good question, calling mock session here sets mock_analyzer.session=mock_session.

snowpark-python/tests/unit/conftest.py

Lines 75 to 82 in 7d4b43c

	@pytest.fixture(scope="module")
	def mock_session(mock_analyzer) -> Session:
	fake_session = mock.create_autospec(Session)
	fake_session._cte_optimization_enabled = False
	fake_session._analyzer = mock_analyzer
	fake_session._plan_lock = mock.MagicMock()
	mock_analyzer.session = fake_session
	return fake_session

this is probably not the best way to do it. open to suggestions.

[sfc-gh-aalam]

same as jamison's question. Linking old response: #2912 (comment)

[sfc-gh-aling]

is this change to pass the new "setter" check?
is mock_query_generator/mock_analyzer used in any of the test code after?

[sfc-gh-aalam]

new_replaced_plan is created by calling within QueryGenerator.to_selectable which uses self as an analyzer.

Before this change Selectable.analyzer would have returned the analyzer used to create the selectable i.e. mock_query_generator.

After this change, Selectable.analyzer will return the appropriate session.analyzer. Therefore, we need to update this test.