On Wed, May 12, 2010 at 11:34 AM, Kevin Grittner <kevin.gritt...@wicourts.gov> wrote: > Pavel Stehule <pavel.steh...@gmail.com> wrote: > >> I would to repeatably update non indexed column of temp table. I >> expected cheap operation, but it isn't true. > > You're updating the row 100000 times within a single transaction. I > don't *think* HOT will reclaim a version of a row until the > transaction which completed it is done and no other transactions can > see that version any longer. It does raise the question, though -- > couldn't a HOT update of a tuple *which was written by the same > transaction* do an "update in place"? I mean, the updating > transaction doesn't need to see the old row after this, and other > transactions shouldn't see it either. > > I suspect that somewhere in the subtransaction or referential > integrity areas there may be some issues with that, but it would be > a clever optimization if it could be pulled off.
scripting this outside of transaction does not exhibit the behavior -- even with autovac off relation size tops out arond 57k. vacuuming as it goes seems to top out around 200 row versions before hot catches them. I guess a good way to think of hot is a page level vacuum. merlin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
