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