On Mon, 23 Oct 2023 15:09:16 -0500 Ken Marshall wrote: >> Hi, >> >> I have a 1.6TB database with over 330 tables on a 4TB NVMe SSD. All >> tables are static (no updates); most in 8M and 33M row sizes. Queries have >> been great, until recently. > >> Also attached is the relevant system journal entries for one query that >> took 2 seconds and two more that took 62 and 52 seconds... Unlike the >> above, these had 3 processes in disk-wait -- see attached screenshot... >> >> I just stopped PG, updated the full backup which was done overnight (so >> the update took about a second), restarted PG and the problem persists... >> >> Any suggestions where to look next? >> >> Thanks, >> Pierre > >Hi Pierre, > >I have seen this type of behavior when parallel queries were enabled and >PostgreSQL decided that a parallel sequential scan query was the fastest >option. Try disabling them and see if that helps. Hi Ken, I'm running a bunch of tests for Adrian right now; but I'm curious: are parallel queries on by default? I have no recollection of ever seeing that was an option. Since I'm only running simple: SELECT count(*) FROM table; does this imply that PG could be breaking the query up in parts to count faster, and why I saw up to 3 processes in D state? Thanks for this tip, Pierre >Regards, >Ken > >
