Re: Re: BUG #12990: Missing pg_multixact/members files (appears to have wrapped, then truncated)

On Thu, May 7, 2015 at 2:00 PM, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
> There's also a question about this function's "else" branch:
>
> void
> MultiXactAdvanceOldest(MultiXactId oldestMulti, Oid oldestMultiDB)
> {
>     if (MultiXactIdPrecedes(MultiXactState->oldestMultiXactId, oldestMulti))
>         SetMultiXactIdLimit(oldestMulti, oldestMultiDB);
>     else
>         DetermineSafeOldestOffset(oldestMulti);
> }
>
> The reason the "else" is there is that I chickened out about not calling
> DetermineSafeOldestOffset() (which SetMultiXactIdLimit calls) when the
> oldestMulti does not advance; what if in the previous run we failed to
> get to this point for whatever reason?  The calls to SetMultiXactIdLimit
> are seldom enough that it seemed better to be protected against previous
> runs not finishing.  Then again, I might be worrying over nothing and
> this is just dead code.

It's dead code for more pedestrian reasons: MultiXactAdvanceOldest()
is called only from xlog_redo(), but does nothing if InRecovery.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company