From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | George Young <gry(at)ll(dot)mit(dot)edu>, pgsql-general(at)postgresql(dot)org, pgsql-sql(at)postgresql(dot)org |
Subject: | Re: [GENERAL] Re: [SQL] bad select performance fixed by forbidding hash joins |
Date: | 1999-07-21 17:57:35 |
Message-ID: | 199907211757.NAA08306@candle.pha.pa.us |
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Lists: | pgsql-general pgsql-sql |
> George Young <gry(at)ll(dot)mit(dot)edu> writes:
> > Yes! PGOPTIONS="-fh" made the query time go from 16 seconds to 2 seconds!
> > Is this a safe thing to leave on permanently, or is there some way to set
> > PGOPTIONS for just this query?
>
> I wouldn't recommend leaving it on as a long-term solution, because
> you're hobbling the system for cases where hashjoin *is* the best
> method. AFAIK there is not a SET VARIABLE method for enabling/disabling
> plan types on-the-fly, though perhaps one should be added.
Postgres does have options to prohibit certain join types, so you could
try forcing a certain join type and see what happens.
--
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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