Fix external reference precharging in datashard read iterators

[snaury]

Changelog entry

...

Changelog category

• Bugfix

Additional information

PR #5758 implemented external reference precharging, which helped to reduce latency bound page faults when reading multiple rows with data stored in external blobs. Unfortunately it turned out to have a bug, where a shard restart could cause ReadActor to retry based on an incorrect state, which would in turn cause missing rows. Since we cannot get the previous iteration key efficiently it's better to never split results across external reference precharging and due a full page fault instead.

Fixes #7769.

[github-actions]

⚪ 2024-09-02 10:06:31 UTC Pre-commit check linux-x86_64-release-clang14 for 59cdebb has started.
⚪ 2024-09-02 10:09:31 UTC ya make is running...
🟢 2024-09-02 10:17:45 UTC Build successful.

[github-actions]

⚪ 2024-09-02 10:14:48 UTC Pre-commit check linux-x86_64-release-asan for 59cdebb has started.
⚪ 2024-09-02 10:17:30 UTC ya make is running...
🔴 2024-09-02 11:49:06 UTC Some tests failed, follow the links below.

Test history | Ya make output

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
10073	10009	0	18	25	21

🟢 2024-09-02 11:49:58 UTC Build successful.
🟢 2024-09-02 11:50:28 UTC ydbd size 5.5 GiB changed* by -5.3 KiB, which is <= 0 Bytes vs main: OK

ydbd size dash	main: 84523e8	merge: 59cdebb	diff	diff %
ydbd size	5 953 683 440 Bytes	5 953 677 992 Bytes	-5.3 KiB	-0.000%
ydbd stripped size	1 489 314 256 Bytes	1 489 313 744 Bytes	-512 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]

⚪ 2024-09-02 10:16:26 UTC Pre-commit check linux-x86_64-relwithdebinfo for 59cdebb has started.
⚪ 2024-09-02 10:19:10 UTC ya make is running...
🟡 2024-09-02 11:25:51 UTC Some tests failed, follow the links below. Going to retry failed tests...

Test history | Ya make output

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
14483	13089	0	16	1360	18

⚪ 2024-09-02 11:27:25 UTC ya make is running... (failed tests rerun, try 2)
🟢 2024-09-02 11:35:25 UTC Tests successful.

Test history | Ya make output

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
33 (only retried tests)	20	0	0	0	13

🟢 2024-09-02 11:35:32 UTC Build successful.
🟡 2024-09-02 11:36:08 UTC ydbd size 8.3 GiB changed* by +715.6 KiB, which is >= 100.0 KiB vs main: Warning

ydbd size dash	main: 1af55df	merge: 59cdebb	diff	diff %
ydbd size	8 915 367 680 Bytes	8 916 100 448 Bytes	+715.6 KiB	+0.008%
ydbd stripped size	481 569 224 Bytes	481 590 920 Bytes	+21.2 KiB	+0.005%

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

[SammyVimes]

LGTM!