On Thu, 2007-12-13 at 11:46 -0600, Kevin Grittner wrote: > >>> On Thu, Dec 13, 2007 at 10:11 AM, in message > <1197562283.4255.1829.camel@xxxxxxxxxx>, Simon Riggs <simon@xxxxxxxxxxxxxxx> > wrote: > > On Thu, 2007-12-13 at 09:46 -0600, Kevin Grittner wrote: > > > >> The data was inserted through a Java program using a prepared > >> statement with no indexes on the table. The primary key was then > >> added, and now I've started a vacuum. The new table wound up being > >> the first big table vacuumed, and I noticed something odd. Even > >> though there have been no rollbacks, updates, or deletes on this > >> table, the vacuum is writing as much as it is reading while dealing > >> with the TOAST data. > > > > Writing hint bits. Annoying isn't it? :-( > > Is there anything in the documentation that mentions this pattern > of activity? Since I started clearing the WAL file tails before > compression, it has surprised me how much WAL file activity there > is from the nightly vacuum. I had assumed that some part of this > was freezing old tuples, but that didn't seem to exactly match the > pattern of activity. If the hint bit changes are written to the > WAL, I think this explains it. They're not. -- Simon Riggs 2ndQuadrant http://www.2ndQuadrant.com ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to majordomo@xxxxxxxxxxxxxx so that your message can get through to the mailing list cleanly
