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.
-- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610)
359-1001+ If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square,
Pennsylvania19073
