On Thu, Jan 5, 2017 at 9:51 AM, Daniel Blanch Bataller <daniel.blanch.bataller@xxxxxxxxx> wrote: > If just recreating the index now it uses it, it might mean that the index > was bloated, that is, it grew so big that it was cheaper a seq scan. > > I’ve seen another case recently where postgres 9.6 wasn’t using the right > index in a query, I was able to reproduce the issue crafting index bigger, > much bigger than it should be. > > Can you record index size as it is now? Keep this info, and If problem > happens again check indexes size, and see if they have grow too much. > > i.e. SELECT relname, relpages, reltuples FROM pg_class WHERE relname = > ‘index_name' > > This might help to see if this is the problem, that indexes are growing too > much for some reason. Are these unique indexes or not? Did Flavio have a workload with many UPDATEs? I ask these questions because I think it's possible that this is explained by a regression in 9.5's handling of index bloat, described here: http://postgr.es/m/CAH2-Wz=SfAKVMv1x9Jh19EJ8am8TZn9f-yECipS9HrrRqSswnA@xxxxxxxxxxxxxx I'm trying to track down cases where this could be an issue, to get a better sense of the problem. -- Peter Geoghegan -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
