Message-ID: <52498D71.8010002@2ndquadrant.it>
Date: Mon, 30 Sep 2013 16:40:49 +0200
From: Giuseppe Broccolo <giuseppe.broccolo@2ndquadrant.it>
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Subject: Re: pg_statio_all_tables columns
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Hi Xenofon,

Il 30/09/2013 14:45, Xenofon Papadopoulos ha scritto:
> I am trying to understand the heap_blks_read and heap_blks_hit of 
> pg_statio_all_tables in 9.2
> Do the numbers refer only to SELECT, or they take INSERT into account?

heap_blks_read and heap_blks_hit refer to number of blocks read from 
disk layer and from page cache respectively during table usage, 
independently if insert, select, delete, update operations are involved.

> Would a heap_blks_read / ( heap_blks_read + heap_blks_hit ) ration of 
> over 55% combined with a heap_blks_read value of over 50M indicate an 
> issue with the queries affecting that table, or it is normal if the 
> table is heavily written to?

High values of this ratio mean you have a well-cached database, since 
disk blocks reads slow down database operations. You can performe it 
increasing the cache available to your database.


Giuseppe.

-- 
Giuseppe Broccolo - 2ndQuadrant Italy
PostgreSQL Training, Services and Support
giuseppe.broccolo@2ndQuadrant.it | www.2ndQuadrant.it


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