On Sat, 2009-01-10 at 11:45 +0000, Simon Riggs wrote: > On Sat, 2009-01-10 at 09:40 +0000, Simon Riggs wrote: > > > This leads to an error when we SubTransSetParent(child_xid, top_xid); > > since this assumes that the top_xid is the parent, which it is not. > > Mostly you wouldn't notice unless you were looking up the subtrans > > status for an xid that had committed but was the child of an aborted > > subtransaction, with the top level xid having > 64 subtransactions. > > It's possible the confusion leads to other bugs in UnobservedXid > > processing, but I didn't look too hard at that. > > > > AFAICS we need both parent and top xids. > > I wonder if its possible to derive the parent by looking at the > highest/most newly assigned xid? Abort records would remove aborted > subtransactions and AFAIK we currently assign a new subtransaction only > ever from the latest current subtransaction. (This wouldn't be > necessarily true if supported true branch-anywhere subtransactions, but > we don't). Sounds correct, but not really sure.
Starting to sound like a do-me-later-if-ever optimisation and certainly nothing I want to rely on in court. I'm progressing with parent_xid added to the xlog record header, for now. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
