[prev in list] [next in list] [prev in thread] [next in thread] 

List:       pgsql-performance
Subject:    Re: Poor Performance running Django unit tests after upgrading from 10.6
From:       Tom Lane <tgl () sss ! pgh ! pa ! us>
Date:       2020-10-15 13:56:12
Message-ID: 3678904.1602770172 () sss ! pgh ! pa ! us
[Download RAW message or body]

Roger Hunwicks <roger@tonic-solutions.com> writes:
> ...
> However, even though we have similar performance for 12.4 for most
> test runs, it remains very variable.
> ...
> I think we have narrowed down the problem to a single, very complex,
> materialized view using CTEs; the unit tests create the test data and
> then refresh the materialized view before executing the actual test
> code.

In addition to others' nearby comments, I'd suggest that running all this
under auto_explain would be informative.  You evidently are not getting a
stable plan for your troublesome query, so you need to see what the range
of plans is, not just probe it once with a manual EXPLAIN.

			regards, tom lane


[prev in list] [next in list] [prev in thread] [next in thread]