Re: BUG #13437: Seq Scan increases heap_blks_read instead of heap_blks_hit when no disk is read

From: Andres Freund <andres(at)anarazel(dot)de>
To: polpot78(at)gmail(dot)com
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #13437: Seq Scan increases heap_blks_read instead of heap_blks_hit when no disk is read
Date: 2015-06-12 13:24:11
Message-ID: 20150612132411.GD28424@awork2.anarazel.de
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On 2015-06-12 13:21:33 +0000, polpot78(at)gmail(dot)com wrote:
> When a seq scan is performed, but no real disk reads is performed, then
> postgreSQL still reports that disk-reads are performed. iostat reports that
> no Blocks are read.

Note that postgres' reports everything as a disk read that goes to the
OS. Which then does it's own level of caching.

Greetings,

Andres Freund

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