Robert Haas <robertmhaas@xxxxxxxxx> writes: > On Sat, Nov 13, 2010 at 10:41 AM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: >> OK, this is an artifact of the "HOT update" optimization. Before >> creating the index, you did updates on the table that would have been >> executed differently if the index had existed. When the index does get >> created, its entries for those updates are incomplete, so the index >> can't be used in transactions that could in principle see the unmodified >> rows. > Is the "in principle" here because there might be an open snapshot > other than the one under which CREATE INDEX is running, like a cursor? Well, the test is based on xmin alone, not cmin, so it can't really tell the difference. It's unclear that it'd be worth trying. regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
