Re: how to know whether query data from memory after pg_prewarm

Le 19/09/2018 à 05:29, Thomas Munro a écrit :
> On Wed, Sep 19, 2018 at 1:35 PM jimmy <mpokky(at)126(dot)com> wrote:
>> I use select pg_prewarm('table1','read','main') to load data of table1 into the memory.
>> when I use select count(1) from table1 group by aa to query data.
>> I find the speed of query is not fast, I wonder whether it query data from memory.
>> And it is slower than Oracle, both of Oracle and Postgresql has same table and count of data.
>> when pg_prewarm use 'read' mode, the data is put into the OS cache, how to examine the table which is pg_prewarmed into the OS cache .
>> I know pg_buffercache ,but it just examine the table in the shared buffer of Postgresql, not the table in the OS cache.
>
> This is a quick and dirty hack, but it might do what you want:
>
> https://github.com/macdice/pgdata_mincore
>
> Tested on FreeBSD, not sure how well it'll travel.

You can use pgfincore extension for that purpose, and more.

https://github.com/klando/pgfincore/blob/master/README.md

--
Cédric Villemain +33 (0)6 20 30 22 52
http://2ndQuadrant.fr/
PostgreSQL: Support 24x7 - Développement, Expertise et Formation