25-2-1: DataShard: don't leave processed checkpoints in the buffer

[snaury]

Changelog entry

Don't leave processed checkpoints in the buffer. Fixes #24779.

Changelog category

• Bugfix

Description for reviewers

[github-actions]

🟢 2025-09-12 14:52:35 UTC The validation of the Pull Request description is successful.

[github-actions]

⚪ 2025-09-12 15:05:08 UTC Pre-commit check linux-x86_64-relwithdebinfo for cc23829 has started.
⚪ 2025-09-12 15:05:24 UTC Artifacts will be uploaded here
⚪ 2025-09-12 15:08:31 UTC ya make is running...
🟢 2025-09-12 16:02:37 UTC Tests successful.

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
26974	25703	0	0	1227	44

🟢 2025-09-12 16:05:05 UTC Build successful.
🟢 2025-09-12 16:05:19 UTC ydbd size 2.2 GiB changed* by +544 Bytes, which is < 100.0 KiB vs stable-25-2-1: OK

ydbd size dash	stable-25-2-1: d25d766	merge: cc23829	diff	diff %
ydbd size	2 324 850 336 Bytes	2 324 850 880 Bytes	+544 Bytes	+0.000%
ydbd stripped size	487 260 648 Bytes	487 260 712 Bytes	+64 Bytes	+0.000%

^{*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]

⚪ 2025-09-12 15:06:17 UTC Pre-commit check linux-x86_64-release-asan for cc23829 has started.
⚪ 2025-09-12 15:06:31 UTC Artifacts will be uploaded here
⚪ 2025-09-12 15:09:29 UTC ya make is running...
🟡 2025-09-12 16:21:18 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet Going to retry failed tests...

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
12791	12598	0	30	121	42

⚪ 2025-09-12 16:22:32 UTC ya make is running... (failed tests rerun, try 2)
🟡 2025-09-12 16:34:47 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet Going to retry failed tests...

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

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
238 (only retried tests)	179	0	4	23	32

⚪ 2025-09-12 16:34:56 UTC ya make is running... (failed tests rerun, try 3)
🟡 2025-09-12 16:47:16 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet

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

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
88 (only retried tests)	33	0	2	22	31

🟢 2025-09-12 16:47:24 UTC Build successful.
🟢 2025-09-12 16:47:47 UTC ydbd size 3.8 GiB changed* by +736 Bytes, which is < 100.0 KiB vs stable-25-2-1: OK

ydbd size dash	stable-25-2-1: 8dd2523	merge: cc23829	diff	diff %
ydbd size	4 045 788 688 Bytes	4 045 789 424 Bytes	+736 Bytes	+0.000%
ydbd stripped size	1 408 532 120 Bytes	1 408 532 248 Bytes	+128 Bytes	+0.000%

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