Refactor assimilation reverse iterating in VDisk

[alexvru]

Changelog entry

Refactor assimilation reverse iterating in VDisk

Changelog category

• Bugfix

Description for reviewers

This patch reworks iteration scheme in Fresh segment, fixing bug #23058

[github-actions]

🟢 2025-08-27 14:51:12 UTC The validation of the Pull Request description is successful.

[github-actions]

⚪ 2025-08-27 14:51:25 UTC Pre-commit check linux-x86_64-release-asan for 298a060 has started.
⚪ 2025-08-27 14:51:39 UTC Artifacts will be uploaded here
⚪ 2025-08-27 14:54:58 UTC ya make is running...
⚫ 2025-08-27 15:06:56 UTC Check cancelled

[github-actions]

⚪ 2025-08-27 14:51:36 UTC Pre-commit check linux-x86_64-relwithdebinfo for 298a060 has started.
⚪ 2025-08-27 14:51:50 UTC Artifacts will be uploaded here
⚪ 2025-08-27 14:55:28 UTC ya make is running...
⚫ 2025-08-27 15:06:53 UTC Check cancelled

[github-actions]

⚪ 2025-08-27 15:07:47 UTC Pre-commit check linux-x86_64-release-asan for 2c43df5 has started.
⚪ 2025-08-27 15:08:13 UTC Artifacts will be uploaded here
⚪ 2025-08-27 15:12:14 UTC ya make is running...
🟡 2025-08-27 17:08:32 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
15488	15043	0	98	314	33

🟢 2025-08-27 17:10:01 UTC Build successful.
🟡 2025-08-27 17:10:33 UTC ydbd size 4.0 GiB changed* by +171.0 KiB, which is >= 100.0 KiB vs main: Warning

ydbd size dash	main: bc5e000	merge: 2c43df5	diff	diff %
ydbd size	4 277 594 008 Bytes	4 277 769 112 Bytes	+171.0 KiB	+0.004%
ydbd stripped size	1 483 437 784 Bytes	1 483 492 056 Bytes	+53.0 KiB	+0.004%

^{*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]

⚪ 2025-08-27 15:12:10 UTC Pre-commit check linux-x86_64-relwithdebinfo for 2c43df5 has started.
⚪ 2025-08-27 15:12:24 UTC Artifacts will be uploaded here
⚪ 2025-08-27 15:15:48 UTC ya make is running...
🟡 2025-08-27 16:37:06 UTC Some tests failed, follow the links below. Going to retry failed tests...

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
38117	35355	0	5	2715	42

⚪ 2025-08-27 16:40:40 UTC ya make is running... (failed tests rerun, try 2)
🟡 2025-08-27 16:55:09 UTC Some tests failed, follow the links below. Going to retry failed tests...

Test history | Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
419 (only retried tests)	381	0	5	0	33

⚪ 2025-08-27 16:55:22 UTC ya make is running... (failed tests rerun, try 3)
🔴 2025-08-27 17:12:08 UTC Some tests failed, follow the links below.

Test history | Ya make output | Test bloat | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
250 (only retried tests)	218	0	5	0	27

🟢 2025-08-27 17:12:16 UTC Build successful.
🟢 2025-08-27 17:12:41 UTC ydbd size 2.3 GiB changed* by +74.6 KiB, which is < 100.0 KiB vs main: OK

ydbd size dash	main: bc5e000	merge: 2c43df5	diff	diff %
ydbd size	2 434 150 168 Bytes	2 434 226 568 Bytes	+74.6 KiB	+0.003%
ydbd stripped size	509 883 976 Bytes	509 890 440 Bytes	+6.3 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}

[github-actions]

⚪ 2025-08-27 17:37:44 UTC Pre-commit check linux-x86_64-release-asan for 802541c has started.
⚪ 2025-08-27 17:37:57 UTC Artifacts will be uploaded here
⚪ 2025-08-27 17:41:21 UTC ya make is running...
🟡 2025-08-27 19:39:26 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
15503	15009	0	132	327	35

🟢 2025-08-27 19:40:50 UTC Build successful.
🟡 2025-08-27 19:41:19 UTC ydbd size 4.0 GiB changed* by +533.3 KiB, which is >= 100.0 KiB vs main: Warning

ydbd size dash	main: 06d55c2	merge: 802541c	diff	diff %
ydbd size	4 277 786 760 Bytes	4 278 332 832 Bytes	+533.3 KiB	+0.013%
ydbd stripped size	1 483 516 568 Bytes	1 483 679 640 Bytes	+159.2 KiB	+0.011%

^{*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]

⚪ 2025-08-27 17:39:57 UTC Pre-commit check linux-x86_64-relwithdebinfo for 802541c has started.
⚪ 2025-08-27 17:40:14 UTC Artifacts will be uploaded here
⚪ 2025-08-27 17:43:43 UTC ya make is running...
🟡 2025-08-27 19:12:07 UTC Some tests failed, follow the links below. Going to retry failed tests...

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
38132	35376	0	2	2715	39

⚪ 2025-08-27 19:15:50 UTC ya make is running... (failed tests rerun, try 2)
🟢 2025-08-27 19:31:02 UTC Tests successful.

Test history | Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
384 (only retried tests)	353	0	0	0	31

🟢 2025-08-27 19:31:12 UTC Build successful.
🟡 2025-08-27 19:31:32 UTC ydbd size 2.3 GiB changed* by +118.6 KiB, which is >= 100.0 KiB vs main: Warning

ydbd size dash	main: 3b87488	merge: 802541c	diff	diff %
ydbd size	2 434 342 064 Bytes	2 434 463 504 Bytes	+118.6 KiB	+0.005%
ydbd stripped size	509 918 472 Bytes	509 933 000 Bytes	+14.2 KiB	+0.003%

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

[mregrock]

LGTM