On Mon, Feb 07, 2022 at 04:56:35PM +0000, Lars Aksel Opsahl wrote: > Sometimes simple sql's like this takes a very long time "select count(*) from information_schema.tables;" > > Other sql's not including system tables may work ok but login also takes a very long time. > > The CPU load on the server is around 25%. There is no iowait. > > This happens typically when we are running many functions in parallel creating many temp tables and unlogged tables I think. > > Here is a slow one: > https://explain.depesz.com/s/tUt5 > > and here is fast one : > https://explain.depesz.com/s/yYG4 The only difference is that this is sometimes many times slower. Finalize Aggregate (cost=42021.15..42021.16 rows=1 width=8) (actual time=50602.755..117201.768 rows=1 loops=1) -> Gather (cost=42020.94..42021.15 rows=2 width=8) (actual time=130.527..117201.754 rows=3 loops=1) Workers Planned: 2 Workers Launched: 2 > Here are my settings (the server has around 256 GB og memory) : What version of postgres ? What OS/version ? https://wiki.postgresql.org/wiki/Slow_Query_Questions Are there any server logs around that time ? Or session logs for the slow query ? Is it because the table creation is locking (rows of) various system catalogs ? I'm not sure if it'd be a single, long delay that you could see easily with log_lock_waits, or a large number of small delays, maybe depending on whether your table creation is done within a transaction. -- Justin
