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Re: cleanup patches for incremental backup

Alexander Lakhin <exclusion@gmail.com>

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From: Alexander Lakhin <exclusion@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>, Nathan Bossart <nathandbossart@gmail.com>
Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2024-01-27T07:00:01Z
Lists: pgsql-hackers 
Hello Robert,

26.01.2024 21:37, Robert Haas wrote:
> On Fri, Jan 26, 2024 at 12:39 PM Nathan Bossart
> <nathandbossart@gmail.com>  wrote:
>> On Fri, Jan 26, 2024 at 11:04:37AM -0500, Robert Haas wrote:
>>> Here is v2 with that addition.
>> Looks reasonable.
> Thanks for the report & review. I have committed that version.

While trying to reproduce the 002_blocks test failure, I've encountered
another anomaly (or two):
make -s check -C src/bin/pg_walsummary/ PROVE_TESTS="t/002*" PROVE_FLAGS="--timer"
# +++ tap check in src/bin/pg_walsummary +++
[05:40:38] t/002_blocks.pl .. # poll_query_until timed out executing this query:
# SELECT EXISTS (
#     SELECT * from pg_available_wal_summaries()
#     WHERE tli = 0 AND end_lsn > '0/0'
# )
#
# expecting this output:
# t
# last actual query output:
# f
# with stderr:
[05:40:38] t/002_blocks.pl .. ok   266739 ms ( 0.00 usr  0.01 sys + 17.51 cusr 26.79 csys = 44.31 CPU)
[05:45:05]
All tests successful.
Files=1, Tests=3, 267 wallclock secs ( 0.02 usr  0.02 sys + 17.51 cusr 26.79 csys = 44.34 CPU)
Result: PASS

It looks like the test may call pg_get_wal_summarizer_state() when
WalSummarizerCtl->initialized is false yet, i. e. before the first
GetOldestUnsummarizedLSN() call.
I could reproduce the issue easily (within 10 test runs) with
pg_usleep(100000L);
added inside WalSummarizerMain() just below:
sigprocmask(SIG_SETMASK, &UnBlockSig, NULL);

But the fact that the test passes regardless of the timeout, make me
wonder, whether any test should fail when such timeout occurs?

Best regards,
Alexander

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Avoid overflow in MaybeRemoveOldWalSummaries().

  2. Revert "Temporary patch to help debug pg_walsummary test failures."

  3. Revise pg_walsummary's 002_blocks test to avoid spurious failures.

  4. Temporary patch to help debug pg_walsummary test failures.

  5. More documentation updates for incremental backup.

  6. Fix typos.

  7. Fix typo.

  8. Try to fix pg_walsummary buildfarm failures.

  9. Repair various defects in dc212340058b4e7ecfc5a7a81ec50e7a207bf288.

  10. Add new pg_walsummary tool.

  11. Add new function pg_get_wal_summarizer_state().

  12. Document WAL summarization information functions.