From: Tom Lane <tgl@sss.pgh.pa.us>
To: SZŰCS Gábor <surrano@mailbox.hu>
Cc: pgsql-performance@postgresql.org
Subject: Re: Query Plan far worse in 7.3.2 than 7.2.1
Date: Tue, 29 Apr 2003 19:05:53 -0400
Message-ID: <18324.1051657553@sss.pgh.pa.us> (raw)
In-Reply-To: <011101c30e68$f056bdb0$0a03a8c0@fejleszt2>
References: <00db01c30e54$1ab272d0$0a03a8c0@fejleszt2>
<26550.1051627993@sss.pgh.pa.us>
<011101c30e68$f056bdb0$0a03a8c0@fejleszt2>
"=?iso-8859-2?B?U1rbQ1MgR+Fib3I=?=" <surrano@mailbox.hu> writes:
> ---------------------------- 7.2.1 PLAN ---------------------------------
> -> Seq Scan on valuta (cost=0.00..1.06 rows=6 width=4) (actual time=0.02..0.11 rows=6 loops=2)
>
> ---------------------------- 7.3.2 PLAN ---------------------------------
> -> Seq Scan on valuta (cost=0.00..20.00 rows=1000 width=4) (actual time=0.02..0.06 rows=6 loops=2)
Ah, there's the problem. You never vacuumed or analyzed "valuta", so
the 7.3 planner didn't know it had only six rows, and chose a plan that
was more appropriate for a larger table. The thousand-row estimate is
the tipoff, because that's the default assumption when there are no
stats.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, surrano@mailbox.hu, pgsql-performance@postgresql.org
Subject: Re: Query Plan far worse in 7.3.2 than 7.2.1
In-Reply-To: <18324.1051657553@sss.pgh.pa.us>
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