On Thu, 2007-12-13 at 10:39 -0600, Kevin Grittner wrote: > >>> On Thu, Dec 13, 2007 at 10:35 AM, in message <13267.1197563721@xxxxxxxxxxxxx>, > Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > > "Kevin Grittner" <Kevin.Grittner@xxxxxxxxxxxx> writes: > >> ... although to a naive user it's not clear what > >> is known at vacuum time that the INSERT into the empty table > >> couldn't have inferred. > > > > The fact that the INSERT actually committed. > > Fair enough. I suppose that the possibility that of access before > the commit would preclude any optimization that would assume the > commit is more likely than a rollback, and do the extra work only in > the unusual case? No chance. There's an optimization of COPY I've not got around to as yet, but nothing straightforward we can do with the normal case. We might be able to have bgwriter set hint bits on dirty blocks, but the success of that would depend upon the transit time of blocks through the cache, i.e. it might be totally ineffective. So might be just overhead for the bgwriter and worse, could divert bgwriter attention away from what its supposed to be doing. That's a lot of work to fiddle with the knobs to improve things and there's higher things on the list AFAICS. -- Simon Riggs 2ndQuadrant http://www.2ndQuadrant.com ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
