Hi, On Sat, Apr 04, 2020 at 10:07:51AM +0300, Andrus wrote: > Hi! > > vacuumdb output: > > vacuumdb: vacuuming database "mydb" > INFO: analyzing "public.mytable" > INFO: "mytable": scanned 2709 of 2709 pages, containing 10834 live rows and > 0 dead rows; 10834 rows in sample, 10834 estimated total rows > > For tables with more than 30000 rows, it shows that there are 30000 rows in sample. > > postgresql.conf does not set default_statistics_target value. > It contains > > #default_statistics_target = 100 # range 1-10000 > > So I expect that there should be 100 rows is sample. > Why Postgres uses 30000 or number of rows in table for smaller tables ? > > Is 30000 some magical value, how to control it. That's because default_statistics_target's unit isn't 1 row but 300 rows, so yeah the 300 here is a little bit of a magical value. You can see more details about this value at https://github.com/postgres/postgres/blob/master/src/backend/commands/analyze.c#L1723-L1756.
