Horton

Re: lastOverflowedXid does not handle transaction ID wraparound

x4mmm@yandex-team.ru

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From: Andrey Borodin <x4mmm@yandex-team.ru>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: Stan Hu <stanhu@gmail.com>, Dmitry Dolgov <9erthalion6@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2021-11-03T08:44:49Z
Lists: pgsql-hackers 

> 21 окт. 2021 г., в 09:01, Kyotaro Horiguchi <horikyota.ntt@gmail.com> написал(а):
> 
> If the discussion so far is correct, the following diff will fix the
> issue.
> 
> diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
> index bd3c7a47fe..19682b73ec 100644
> --- a/src/backend/storage/ipc/procarray.c
> +++ b/src/backend/storage/ipc/procarray.c
> @@ -4463,6 +4463,12 @@ ExpireOldKnownAssignedTransactionIds(TransactionId xid)
> {
>        LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
>        KnownAssignedXidsRemovePreceding(xid);
> +       /*
> +        * reset lastOverflowedXid if we know transactions that have been possiblly
> +        * running are being gone.
> +        */
> +       if (TransactionIdPrecedes(procArray->lastOverflowedXid, xid))
> +               procArray->lastOverflowedXid = InvalidTransactionId;
>        LWLockRelease(ProcArrayLock);
> }

The patch seems correct bugfix to me. The only question I have: is it right place from modularity standpoint? procArray->lastOverflowedXid is not a part of KnownAssignedTransactionIds?

Best regards, Andrey Borodin.

Commits

  1. Reset lastOverflowedXid on standby when needed

  2. Fix variable shadowing in procarray.c.

  3. Move InRecovery and standbyState global vars to xlogutils.c.