Add return_not_null_data_as_optional parameter to read_table

[krasnovdm]

Problem

read_table always returns NOT NULL columns wrapped in Optional, and there is no way to opt out in the Python SDK.

The gRPC ReadTableRequest already has a return_not_null_data_as_optional field, and the C++ SDK exposes it via TReadTableSettings().ReturnNotNullAsOptional(false). The Python SDK simply never set this field, so users reading a table with NOT NULL columns always get Optional values back.

Change

Add a return_not_null_data_as_optional parameter to read_table (sync ydb/table.py and async ydb/aio/table.py) and plumb it through read_table_request_factory. It accepts a bool (mapped to FeatureFlag.ENABLED/DISABLED) or a raw FeatureFlag.Status.

Default behavior is unchanged: when the parameter is not provided, the field is left unset and NOT NULL columns are still returned as Optional (backward compatible).

# opt out of the Optional wrapping for NOT NULL columns:
session.read_table(path, return_not_null_data_as_optional=False)

[vgvoleg]

hi! please update your branch to latest main and add some tests

[krasnovdm]

Thanks for the review! Done:

• Rebased the branch onto the latest main (resolved the CHANGELOG conflict; mergeable should be clean now).
• Added unit tests in tests/table/test_read_table_request.py covering read_table_request_factory for return_not_null_data_as_optional=True/False and the default (unset) case.

PTAL 🙏

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.36%. Comparing base (3688a5f) to head (56c508d).

Files with missing lines	Patch %	Lines
ydb/_session_impl.py	66.66%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #880   +/-   ##
=======================================
  Coverage   82.36%   82.36%           
=======================================
  Files          99       99           
  Lines       12753    12759    +6     
  Branches     1242     1245    +3     
=======================================
+ Hits        10504    10509    +5     
- Misses       1795     1796    +1     
  Partials      454      454           

Flag	Coverage Δ
integration	80.15% <0.00%> (-0.04%)	⬇️
unit	48.72% <66.66%> (+0.14%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
ydb/aio/table.py	80.32% <ø> (ø)
ydb/table.py	66.69% <ø> (ø)
ydb/_session_impl.py	61.53% <66.66%> (+0.42%)	⬆️

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[vgvoleg]

@krasnovdm please fix ci checks.

[krasnovdm]

@vgvoleg pushed a fix for the failing lint jobs — reformatted tests/table/test_read_table_request.py with black==25.11.0 (the test file I added had multi-line calls that black collapses). black --check and flake8 are clean locally now. PTAL.

[krasnovdm]

Rebased onto latest main (resolved the CHANGELOG.md conflict — both unreleased bullets kept) and fixed the failing lint. All checks are green now: lint (black/style/mypy), unit pass. The PR is MERGEABLE. Only your earlier change request is left blocking it — could you re-review / dismiss the stale CHANGES_REQUESTED? PTAL 🙏 cc @Ovcharuk

[krasnovdm]

Small follow-up: moved the unit tests into the existing ydb/table_test.py (and dropped the separate tests/table/ file) to align with AGENTS.md — unit tests live in ydb/*_test.py and should extend existing files. Squashed to a single commit. CI is green (lint/unit/mypy), still MERGEABLE.