George Dunlap writes ("Re: [OSSTEST PATCH 06/14] sg-report-flight: Use WITH
clause to use index for $anypassq"):
> > On Jul 21, 2020, at 7:41 PM, Ian Jackson <[email protected]> wrote:
> > + # In psql 9.6 this WITH clause makes postgresql do the steps query
> > + # first. This is good because if this test never passed we can
> > + # determine that really quickly using the new index, without
> > + # having to scan the flights table. (If the test passed we will
> > + # probably not have to look at many flights to find one, so in
> > + # that case this is not much worse.)
>
> Seems a bit weird, but OK. The SQL looks the same, so:
>
> Reviewed-by: George Dunlap <[email protected]>
Thanks. This business with the WITH clause as an optimisation fence
is well-known in Postgres circles, it seems.
Ian.
