Re: pg_statio_all_tables columns

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