On 23/06/2020 14:42, Klaudie Willis wrote: > I got my first hint of why this problem occurs when I looked at the > statistics. For the column in question, "instrument_ref" the statistics > claimed it to be: > > The default_statistics_target=500, and analyze has been run. > select * from pg_stats where attname like 'instr%_ref'; -- Result: *40.000* > select count(distinct instrumentid_ref) from bigtable -- Result: *33 385 922 > (!!)* > > That is an astonishing difference of almost a 1000X. >
I think you are counting 2 different things here. The first query returns all the columns "like 'instr%_ref'" present in the statistics (so in the whole cluster), while the second is counting the actual number of different rows in bigtable. regards, fabio pardi
