Re: pg_statio_all_tables columns

Hello Giuseppe,
do you actually mean I have a *poorly-cached *database?
Should this ratio stay low even in the case of a write-heavy table?

On Mon, Sep 30, 2013 at 5:40 PM, Giuseppe Broccolo <
giuseppe(dot)broccolo(at)2ndquadrant(dot)it> wrote:

> 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(dot)broccolo(at)2ndQuadrant(dot)**it | www.2ndQuadrant.it
>
>
>
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