On Tue, 25 Aug 2020 at 22:10, iulian dragos <iulian.dragos@xxxxxxxxxxxxxx> wrote: > Thanks for the tip! Indeed, `n_distinct` isn't right. I found it in pg_stats set at 131736.0, but the actual number is much higher: 210104361. I tried to set it manually, but the plan is still the same (both the actual number and a percentage, -0.4, as you suggested): You'll need to run ANALYZE on the table after doing the ALTER TABLE to change the n_distinct. The ANALYZE writes the value to pg_statistic. ALTER TABLE only takes it as far as pg_attribute's attoptions. ANALYZE reads that column to see if the n_distinct estimate should be overwritten before writing out pg_statistic Just remember if you're hardcoding a positive value that it'll stay fixed until you change it. If the table is likely to grow, then you might want to reconsider using a positive value and consider using a negative value as mentioned in the doc link. David
