Re: Hot Standby dev build (v8) - Mailing list pgsql-hackers

On Fri, 2009-01-16 at 16:33 +0200, Heikki Linnakangas wrote:
> I don't think RecentGlobalXmin is good enough here:
> 
> > !             /*
> > !              * We would like to set an accurate latestRemovedXid, but there
> > !              * is no easy way of obtaining a useful value. So we use the
> > !              * probably far too conservative value of RecentGlobalXmin instead.
> > !              */
> > !             xlrec_delete.latestRemovedXid = RecentGlobalXmin;
> > !             rdata[0].data = (char *) &xlrec_delete;
> > !             rdata[0].len = SizeOfBtreeDelete;
> 
> RecentGlobalXmin is just a hint, it lags behind the real oldest xmin 
> that GetOldestXmin() would return. If another backend has a more recent 
> RecentGlobalXmin value, and has killed more recent tuples on the page, 
> the latestRemovedXid written here is too old.

What do you think we should do instead?

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support