On Thursday, June 21, 2012 03:56:54 PM Florian Pflug wrote: > On Jun21, 2012, at 13:41 , Andres Freund wrote: > > 3b) > > Ensure that enough information in the catalog remains by fudging the xmin > > horizon. Then reassemble an appropriate snapshot to read the catalog as > > the tuple in question has seen it. > > The ComboCID machinery makes that quite a bit harder, I fear. If a tuple is > updated multiple times by the same transaction, you cannot decide whether a > tuple was visible in a certain snapshot unless you have access to the > updating backend's ComboCID hash. Thats a very good point. Not sure how I forgot that.
It think it might be possible to reconstruct a sensible combocid mapping from the walstream. Let me think about it for a while... Andres -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
