Horton

Re: XID formatting and SLRU refactorings

Alexander Korotkov <aekorotkov@gmail.com>

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From: Alexander Korotkov <aekorotkov@gmail.com>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Aleksander Alekseev <aleksander@timescale.com>, Postgres hackers <pgsql-hackers@lists.postgresql.org>, Pavel Borisov <pashkin.elfe@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Maxim Orlov <orlovmg@gmail.com>, Japin Li <japinli@hotmail.com>, Andres Freund <andres@anarazel.de>, Michael Paquier <michael@paquier.xyz>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Date: 2023-12-17T15:22:23Z
Lists: pgsql-hackers

Attachments

On Sun, Dec 17, 2023 at 1:48 AM Thomas Munro <thomas.munro@gmail.com> wrote:
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=loach&dt=2023-12-16%2005%3A25%3A18
>
> TRAP: failed Assert("epoch > 0"), File: "twophase.c", Line: 969, PID: 71030
> 0xa8edcd <ExceptionalCondition+0x6d> at
> /usr/home/pgbf/buildroot/HEAD/pgsql.build/tmp_install/home/pgbf/buildroot/HEAD/inst/bin/postgres
> 0x613863 <ReadTwoPhaseFile+0x463> at
> /usr/home/pgbf/buildroot/HEAD/pgsql.build/tmp_install/home/pgbf/buildroot/HEAD/inst/bin/postgres
>
> That's the new assertion from 5a1dfde8:
>
> + * The wrap logic is safe here because the span of active xids cannot
> exceed one
> + * epoch at any given time.
> ...
> +       if (unlikely(xid > nextXid))
> +       {
> +               /* Wraparound occured, must be from a prev epoch. */
> +               Assert(epoch > 0);

Thank you for noticing this.  I did some investigations.
AdjustToFullTransactionId() uses TransamVariables->nextXid to convert
TransactionId into FullTransactionId.  However,
ProcArrayApplyRecoveryInfo() first checks two phase transactions then
updates  TransamVariables->nextXid.  Please, see the draft patch
fixing this.  I'll do further check if it has some side-effects.

------
Regards,
Alexander Korotkov

Commits

  1. Fix more holes with SLRU code in need of int64 for segment numbers

  2. Use more consistently int64 for page numbers in SLRU-related code

  3. Improve comments in slru.{c,h} about segment name format

  4. Reorder actions in ProcArrayApplyRecoveryInfo()

  5. Fix typo in 5a1dfde8334b

  6. Fix warning due non-standard inline declaration in 4ed8f0913bfdb5f355

  7. Add SLRU tests for 64-bit page case

  8. Make use FullTransactionId in 2PC filenames

  9. Use larger segment file names for pg_notify

  10. Index SLRUs by 64-bit integers rather than by 32-bit integers

  11. Keep track of transaction commit timestamps

  12. Handle 5-char filenames in SlruScanDirectory