From: Tom Lane <tgl@sss.pgh.pa.us>
To: kynn@panix.com
Cc: pgsql-performance@postgresql.org
Subject: Re: Optimizing a huge_table/tiny_table join
Date: Wed, 24 May 2006 21:41:59 -0400
Message-ID: <7082.1148521319@sss.pgh.pa.us> (raw)
In-Reply-To: <200605250052.k4P0qrT11965@panix3.panix.com>
References: <200605250052.k4P0qrT11965@panix3.panix.com>
<kynn@panix.com> writes:
> Limit (cost=19676.75..21327.99 rows=6000 width=84)
> -> Hash Join (cost=19676.75..1062244.81 rows=3788315 width=84)
> Hash Cond: (upper(("outer".id)::text) = upper(("inner".id)::text))
> -> Seq Scan on huge_table h (cost=0.00..51292.43 rows=2525543 width=46)
> -> Hash (cost=19676.00..19676.00 rows=300 width=38)
> -> Seq Scan on tiny_table t (cost=0.00..19676.00 rows=300 width=38)
Um, if huge_table is so much bigger than tiny_table, why are the cost
estimates for seqscanning them only about 2.5x different? There's
something wacko about your statistics, methinks.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, kynn@panix.com
Subject: Re: Optimizing a huge_table/tiny_table join
In-Reply-To: <7082.1148521319@sss.pgh.pa.us>
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