Generally when it comes to query performance, I check how the vacuuming and statistics collection is performed on Tables and Indexes hit by the query.
Apart from the above i check the code logic ( for any bad joins ) and column statistics as well.
I got hold of two catalog tables "pg_stats" and "pg_class".
Column "avg_width" and "distinct" in pg_stats gets me lot of sensible information regarding, column values and size of the column.
Can someone help me know when the values in these columns are bound to change ? Is it only when ANALYZE runs ?
I am about to calculate lot of metrics depending on above values. Please help !
Thanks
Venkat
