fix: schema version handling

[Enjection]

Changelog entry

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Changelog category

• New feature
• Experimental feature
• Improvement
• Performance improvement
• User Interface
• Bugfix
• Backward incompatible change
• Documentation (changelog entry is not required)
• Not for changelog (changelog entry is not required)

Description for reviewers

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[github-actions]

🟢 2025-11-08 02:06:28 UTC The validation of the Pull Request description is successful.

[github-actions]

⚪ 2025-11-08 23:06:32 UTC Pre-commit check linux-x86_64-release-asan for 39d650c has started.
⚪ 2025-11-08 23:06:50 UTC Artifacts will be uploaded here
⚪ 2025-11-08 23:09:04 UTC ya make is running...
🟡 2025-11-09 01:06:32 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet

Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
15664	15281	0	138	221	24

🟢 2025-11-09 01:06:46 UTC Build successful.
🟢 2025-11-09 01:07:13 UTC ydbd size 3.8 GiB changed* by +32.2 KiB, which is < 100.0 KiB vs main: OK

ydbd size dash	main: 61c53ab	merge: 39d650c	diff	diff %
ydbd size	4 079 105 736 Bytes	4 079 138 760 Bytes	+32.2 KiB	+0.001%
ydbd stripped size	1 513 384 136 Bytes	1 513 395 016 Bytes	+10.6 KiB	+0.001%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}

[github-actions]

⚪ 2025-11-08 23:06:41 UTC Pre-commit check linux-x86_64-relwithdebinfo for 39d650c has started.
⚪ 2025-11-08 23:06:59 UTC Artifacts will be uploaded here
⚪ 2025-11-08 23:09:16 UTC ya make is running...
🟡 2025-11-09 00:46:15 UTC Some tests failed, follow the links below. Going to retry failed tests...

Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
39267	36432	0	6	2803	26

⚪ 2025-11-09 00:46:34 UTC ya make is running... (failed tests rerun, try 2)
🟢 2025-11-09 00:58:41 UTC Tests successful.

Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
79 (only retried tests)	62	0	0	0	17

🟢 2025-11-09 00:58:49 UTC Build successful.
🟢 2025-11-09 00:59:09 UTC ydbd size 2.3 GiB changed* by +21.7 KiB, which is < 100.0 KiB vs main: OK

ydbd size dash	main: 61c53ab	merge: 39d650c	diff	diff %
ydbd size	2 436 051 328 Bytes	2 436 073 536 Bytes	+21.7 KiB	+0.001%
ydbd stripped size	517 306 128 Bytes	517 311 568 Bytes	+5.3 KiB	+0.001%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}

[Copilot]

Pull Request Overview

This PR refactors and enhances the version synchronization logic for continuous backup CDC streams, particularly for tables with indexes. The refactoring extracts inline logic into separate functions and adds support for syncing index entity versions during continuous backup operations.

• Introduces a new PersistTableIndexAlterVersion function to persist index alter versions to the database
• Refactors version synchronization logic into dedicated helper functions with improved structure and logging
• Adds a test case for CDC version synchronization with multiple tables and indexes

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
ydb/core/tx/schemeshard/schemeshard_impl.h	Declares new PersistTableIndexAlterVersion function for persisting index alter versions
ydb/core/tx/schemeshard/schemeshard_impl.cpp	Implements the new persistence function for table index alter versions
ydb/core/tx/schemeshard/schemeshard__operation_common_cdc_stream.cpp	Refactors version synchronization logic into helper functions and adds support for syncing child indexes during continuous backup operations
ydb/core/tx/datashard/datashard_ut_incremental_backup.cpp	Adds a new test case CdcVersionSync for testing continuous backup with multiple indexed tables

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[Copilot]

[nitpick] The condition on line 208-209 is complex with multiple boolean checks. Consider extracting this into a descriptive helper function like ShouldSyncWithParentTable to improve readability and maintainability.