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.broccolo@xxxxxxxxxxxxxx> wrote:
Hi Xenofon,
Il 30/09/2013 14:45, Xenofon Papadopoulos ha scritto: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.
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?
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.
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?
Giuseppe.
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Giuseppe Broccolo - 2ndQuadrant Italy
PostgreSQL Training, Services and Support
giuseppe.broccolo@2ndQuadrant.it | www.2ndQuadrant.it
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