Re: mysterious difference in speed when combining two queries with OR

am Wed, dem 23.04.2008, um 9:58:10 +0200 mailte A. Kretschmer folgendes:
> > Query A (two queries)
> >
> > select distinct moment.mid from moment,timecard where parent = 45 and (pid=17 and timecard.mid = moment.mid) order by moment.mid;
> > select distinct moment.mid from moment,timecard where parent = 45 and (pbar = 0) order by moment.mid;
> >
> > Query B (combining the two with OR)
> >
> > select distinct moment.mid from moment,timecard where parent = 45 and ((pid=17 and timecard.mid = moment.mid) or (pbar = 0)) order by moment.mid;

Thanks to depesz on #postgresql (irc-channel):

Query A, the second query: there are no join between the 2 tables.
Mistake?

Andreas
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Andreas Kretschmer
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