Re: Multiple Xids in PGPROC?

Christopher Kings-Lynne wrote:
> > I remember going through this.  Other backends will use pg_subtrans to
> > know what transactions are in progress. They have to do the standard
> > lookups to find the status of the parent transaction.  The backend-local
> > list of xids is needed so the commit can clean up those subtransaction
> > xids so that later transactions don't have to use pg_subtrans.
> 
> Is there some solution whereby the common case (99.999% of transactions 
> won't be subtransactoins) is fast, and the uncommon case of being in a 
> subtransaction is slower?

Yes, we use an unreserved clog status to indicate a pg_subtrans lookup
is required.  In non-subtrans cases, no pg_subtrans lookup is required.

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