Adrian, you are correct. My mistanke. K ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Tuesday, June 23, 2020 4:14 PM, Adrian Klaver <adrian.klaver@xxxxxxxxxxx> wrote: > On 6/23/20 7:05 AM, Fabio Pardi wrote: > > > 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. > > I believe the OP actually meant the query to be: > > select n_distinct from pg_stats where attname like 'instr%_ref'; > > > regards, > > fabio pardi > > -- > > Adrian Klaver > adrian.klaver@xxxxxxxxxxx
