On 2014-04-03 13:38:29 +0300, Heikki Linnakangas wrote: > On 04/01/2014 08:58 PM, Andres Freund wrote: > >On 2014-04-01 12:56:04 -0500, Jim Nasby wrote: > >>On 3/4/14, 8:50 AM, Andres Freund wrote: > >>>Can't that be solved by just creating the permanent relation in a new > >>>relfilenode? That's equivalent to a rewrite, yes, but we need to do that > >>>for anything but wal_level=minimal anyway. > >> > >>Maybe I'm missing something, but doesn't this actually involve writing the > >>data twice? Once into WAL and again into the relation itself? > > > >Yes. But as I said, that's unavoidable for anything but > >wal_level=minimal. > > Ideally, you would *only* write the data to WAL, when you do ALTER TABLE ... > SET LOGGED. There's no fundamental reason you need to rewrite the > heap, too.
As another point: What's the advantage of that? The amount of writes will be the same, no? It doesn't seem to be all that interesting that a second filenode exists temporarily? Greetings, Andres Freund -- 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
