Alessandro Manzoni <manzoni.alessandro4@xxxxxxxxx> writes: > Then I have a complex query that has two complete different > performances, in these two cases: > case a) > with getfieldone as (select * from tableone where fieldone = 'one') > select * from getfieldone > inner join tabletwo on ... [and other joins] > case b) > select * from viewone > inner join tabletwo on ... [and other joins, the same as case a)] > I expected the same performance, but case a) lasts a few hundreds ms, > while case b) lasts more than 12 seconds. WITH is an optimization fence (at present --- there is discussion of relaxing that) so it's not exactly surprising that these queries perform differently. I am a little surprised though that case a) is the faster one; usually, preventing the planner from optimizing the whole query as one problem makes things worse. Saying more than that would require a lot more detail. https://wiki.postgresql.org/wiki/Slow_Query_Questions regards, tom lane
