> Is one of those estimates way off reality, or is it only the conjunction which is deranged?
The estimate is wrong *even with a single tag*, without the conjunction (e.g. expected 3500, actual 20). Then the conjunction can make the bias even worse... On Sun, Feb 2, 2020 at 3:23 PM Justin Pryzby <pry...@telsasoft.com> wrote: > On Sun, Feb 02, 2020 at 03:18:19PM +0100, Marco Colli wrote: > > Hello! > > > > Let's say that you have a simple query like the following on a large > table > > (for a multi-tenant application): > > SELECT "subscribers".* FROM "subscribers" WHERE > "subscribers"."project_id" > > = 123 AND (tags @> ARRAY['de']::varchar[]); > > > > If you run EXPLAIN ANALYZE you can see that stats are completely wrong. > > For example I get an expected count of 3,500 rows whereas the actual > > result is 20 rows. This also results in bad query plans... > > > https://www.postgresql.org/message-id/CAMkU%3D1z%2BQijUWAYgeqeyw%2BAvD7adPgOmEnY%2BOcTw6qDVFtD7cQ%40mail.gmail.com > On Fri, Jan 10, 2020 at 12:12:52PM -0500, Jeff Janes wrote: > > Why is the estimate off by so much? If you run a simple select, what the > > actual and expected number of rows WHERE project_id = 12345? WHERE tags > @> > > '{crt:2018_11}'? Is one of those estimates way off reality, or is it > only > > the conjunction which is deranged? > > Could you respond to Jeff's inquiry ? > > Justin >
