Jeremiah, > Thanks to all, I had already run analyze. But the STATISTICS setting > seems to have worked. I'm just not sure what it did..? Would anyone care > to explain.
The STATISTICS setting improves the granularity of statistics kept by the query planner on that column; increasing the granularity (i.e. more random samples) can significantly improve things in cases where you have data whose distribution is significantly skewed. Certainly whenever you see the query planner using a slow nestloop becuase of a bad row-return estimate, it is one of the first things to try. Its drawbacks are 4-fold: 1) to keep it working, you will probably need to run ANALZYE more often than you have been; 2) these ANALYZEs will take longer, and have the annoying side effect of flooring your CPU while they do; 3) You will have to be sure that your vacuum plan includes vacuuming the pg_statistic table as the database superuser, as that table will be getting updated more often. 4) Currently, pg_dump does *not* back up statistics settings. So you will need to save a script which does this in preparation for having to restore your database. Which is why the stats are set low by default. -- Josh Berkus Aglio Database Solutions San Francisco ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
