2015-10-21 19:55 GMT+02:00 Jamie Koceniak <jkocen...@mediamath.com>: > Hi Pavel, > > > > Thanks for the reply. > > > > 1. The queries aren’t waiting on any locks. > > The query has a recursive join that uses a table with only 80k records and > that table is not updated often. > > > > 2. The I/O load was not high. CPU utilization was very high and load was > very high. > > We have a large effective_cache_size = 512GB (25% of total memory) >
so your server has 2TB RAM? It is not usual server - so this issue can be pretty strange :( What is size of shared memory? Probably is significantly lower than effective_cache_size? Try to reduce effective cache size to be lower than shared buffers Regards Pavel > > > Thanks, > > Jamie > > > > *From:* Pavel Stehule [mailto:pavel.steh...@gmail.com] > *Sent:* Wednesday, October 21, 2015 12:04 AM > *To:* Jamie Koceniak > *Cc:* pgsql-performance@postgresql.org > *Subject:* Re: [PERFORM] Recursive query performance issue > > > > Hi > > > > 2015-10-20 19:34 GMT+02:00 Jamie Koceniak <jkocen...@mediamath.com>: > > Version: > > > ----------------------------------------------------------------------------------------------- > > PostgreSQL 9.1.14 on x86_64-unknown-linux-gnu, compiled by gcc (Debian > 4.7.2-5) 4.7.2, 64-bit > > > > Query Plan > > http://explain.depesz.com/s/4s37 > > > > Normally, this query takes around 200-300 ms to execute. > > However when several queries are run concurrently, query performance drops > to 30-60 seconds. > > > > > > there can be few reasons: > > 1. locking - are you sure, so your queries don't wait on locks? > > 2. issues with cache stability - is there high IO load? You can try to > increase effective_cache_size (or decrease if you have not enough memory) > > Regards > > Pavel > > > > > > >
