From: Laurenz Albe <laurenz.albe@cybertec.at> Sent: Friday, October 21, 2022 8:56 PM To: Julie Nishimura <juliezain@hotmail.com>; pgsql-general@postgresql.org <pgsql-general@postgresql.org> Subject: Re: constantly updated table in Amazon RDS
On Fri, 2022-10-21 at 18:51 +0000, Julie Nishimura wrote: > A table is constantly updated by inserting new rows. Will it affect select if where clause is based on > date? > Does "where clause" to specify > date and < now?
Potentially yes, if the rows you query are the most recent rows, for which PostgreSQL has the least accurate statistics. There is a heuristics in the PostgreSQL optimizer: it looks for the actual maximal value to adjust the last histogram bucket boundary.
If that is not enough, you can get PostgreSQL to gather table statistics more often by lowering "autovacuum_analyze_scale_factor" for that table:
ALTER TABLE tab SET (autovacuum_analyze_scale_factor = 0.01);