2010/5/25 Chirag Dave <cdave@xxxxxxxxxxxxxxx>: > > > On Tue, May 25, 2010 at 1:48 PM, Balkrishna Sharma <b_ki@xxxxxxxxxxx> wrote: >> >> Hi, >> I am increasing the shared_buffer size in postgresql.conf and want to >> measure its effect on READ. In essence I want to know if the SELECT queries >> I am firing repeatedly is reading from the buffer or going directly to the >> disk. >> I am expecting the first SELECT to go to disk and the subsequent call of >> the same SELECT to read from buffer . >> Right now I am just looking at execution time of the SELECTs and trying to >> conclude. But there should be a direct way to see where the SELECT reads >> from. > > You can also use pg_stat_database view. you can compute cache reads > percentage of the total number of reads (cache and physical) between the two > snapshots using pg_stat_database.blks_hit and pg_stat_database.blks_read. views does not reflect this exact behavior : hit and read are relative to hit shared buffers and request a block (from OS page cache or from disk). > > Chirag Dave 416-673-4102 > Database Administrator, Afilias Canada Corp. > cdave@xxxxxxxxxxxxxxx > > >> >> How can I accomplish this ? >> Thanks >> Bala >> ________________________________ >> The New Busy think 9 to 5 is a cute idea. Combine multiple calendars with >> Hotmail. Get busy. > -- Cédric Villemain 2ndQuadrant http://2ndQuadrant.fr/ PostgreSQL : Expertise, Formation et Support -- Sent via pgsql-admin mailing list (pgsql-admin@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin
