On Tue, Nov 12, 2013 at 2:47 PM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> > That's right, we store 90 days and roll up data older than that into a > > different table. > > Ah-hah. The default statistics target is 100, so indeed ANALYZE is going > to be able to fit every date entry in the table into the > most-common-values list. In this situation, you'd rather that there were > some uncertainty left. Given that the distribution of the date column is > (I assume) pretty level, you don't really need full information about this > column. I'd try backing off the stats target for the date column (and > only the date column --- see ALTER TABLE SET STATISTICS) to 50 or even > less. That was it! I set it to 50 on all the 90-days tables and now we no longer see that regular increase in disk reads between midnight of the new day and the 1:37am re-analyze. Thanks!
