From: Alex Turner <armtuk@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Pgsql-Performance ((E-mail)) <pgsql-performance@postgresql.org>
Subject: Re: Confusion and Questions about blocks read
Date: Fri, 22 Sep 2006 13:13:41 -0400
Message-ID: <33c6269f0609221013g658e19b0lfe57e392c77cf6d0@mail.gmail.com> (raw)
In-Reply-To: <780.1158942275@sss.pgh.pa.us>
References: <33c6269f0609220834x6c10db9xa40d6121825dfd14@mail.gmail.com>
<780.1158942275@sss.pgh.pa.us>
ahh.... good point
Thanks
On 9/22/06, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> "Alex Turner" <armtuk@gmail.com> writes:
> > Home come the query statistics showed that 229066 blocks where read
> given
> > that all the blocks in all the tables put together only total 122968?
>
> You forgot to count the indexes. Also, the use of indexscans in the
> mergejoins probably causes multiple re-reads of some table blocks,
> depending on just what the physical ordering of the rows is.
>
> regards, tom lane
>
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To: pgsql-performance@postgresql.org
Cc: armtuk@gmail.com, tgl@sss.pgh.pa.us
Subject: Re: Confusion and Questions about blocks read
In-Reply-To: <33c6269f0609221013g658e19b0lfe57e392c77cf6d0@mail.gmail.com>
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