Re: MultiXact truncation, startup et al. - Mailing list pgsql-hackers

On 2013-11-29 12:49:32 -0300, Alvaro Herrera wrote:
> + * - xidFullScanLimit (also known as the table freeze age) represents the
> + *   minimum Xid age past which a vacuum will be turned into a full-table one,
> + *   to freeze tuples across the whole table.  Vacuuming a table younger than
> + *   this can use a partial scan.

Imo "age" isn't really appropriate, since it's a concrete xid that's the
cutoff. It's determined by vacuum_freeze_table_age, sure, but at that
point it's an absolute value.

> + * - mxactFullScanLimit (as xidFullScanLimit) represents the minimum MultiXact
> + *   age past which a vacuum will be turned into a full-table one, as with
> + *   xidFullScanLimit.

Not an age again.


> +    scan_all |= MultiXactIdPrecedesOrEquals(onerel->rd_rel->relminmxid,
> +                                            mxactFullScanLimit);

Hah. That's cute ;).
> @@ -1906,6 +1931,7 @@ CheckPointMultiXact(void)
>      SimpleLruFlush(MultiXactOffsetCtl, true);
>      SimpleLruFlush(MultiXactMemberCtl, true);
>  
> +
>      TRACE_POSTGRESQL_MULTIXACT_CHECKPOINT_DONE(true);
>  }

My fault, but superflous newline added.

> @@ -8619,6 +8623,22 @@ CreateRestartPoint(int flags)
>      }
>      LWLockRelease(ControlFileLock);
>  
> +

Also an inconsistent newline, again by me :(

> -            multi = HeapTupleHeaderGetRawXmax(tuple);
> -            if (MultiXactIdPrecedes(multi, cutoff_multi))
> -                return true;
> +            nmembers = GetMultiXactIdMembers(xid, &members, true);
> +            for (i = 0; i < nmembers; i++)
> +            {
> +                TransactionId member = members[i].xid;
> +                Assert(TransactionIdIsNormal(member));
> +
> +                /* we don't care about lockers */
> +                if (ISUPDATE_from_mxstatus(members[i].status))
> +                    continue;

Isn't there a ! missing?

> diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
> index c389bf3..518c22d 100644
> --- a/src/backend/access/transam/multixact.c
> +++ b/src/backend/access/transam/multixact.c
> @@ -445,6 +445,10 @@ MultiXactIdExpand(MultiXactId multi, TransactionId xid, MultiXactStatus status)
>  
>      for (i = 0, j = 0; i < nmembers; i++)
>      {
> +        /*
> +         * FIXME: is it possible that we copy over too old updater xids
> +         * here?
> +         */
>          if (TransactionIdIsInProgress(members[i].xid) ||
>              ((members[i].status > MultiXactStatusForUpdate) &&
>               TransactionIdDidCommit(members[i].xid)))

That's not really a new thing though, so I am fine with leaving that as
is for now.

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services