On 2019-Nov-05, Tatsuro Yamada wrote: > ============== > [Session1] > \! pgbench -i > create statistics pg_ext1 (dependencies) ON aid, bid from pgbench_accounts; > create statistics pg_ext2 (mcv) ON aid, bid from pgbench_accounts; > create statistics pg_ext3 (ndistinct) ON aid, bid from pgbench_accounts;
Wow, it takes a long time to compute these ... Hmm, you normally wouldn't define stats that way; you'd do this instead: create statistics pg_ext1 (dependencies, mcv,ndistinct) ON aid, bid from pgbench_accounts; I'm not sure if this has an important impact in practice. What I'm saying is that I'm not sure that "number of ext stats" is necessarily a useful number as shown. I wonder if it's possible to count the number of items that have been computed for each stats object. So if you do this create statistics pg_ext1 (dependencies, mcv) ON aid, bid from pgbench_accounts; create statistics pg_ext2 (ndistinct,histogram) ON aid, bid from pgbench_accounts; then the counter goes to 4. But I also wonder if we need to publish _which_ type of ext stats is currently being built, in a separate column. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
