Re: PostgreSQL Caching - Mailing list pgsql-performance

        Thanks,

        I wonder these ;

        * When any session updates the data that allready in shared buffer,
does Postgres sychronize the data both disk and shared buffers area
immediately ?
        * Does postgres cache SQL execution plan analyze results in memory
to use for other sessions ? For example ;
        When session A execute "SELECT * FROM tab WHERE col1 = val1 AND col2
= val2", does postgres save the parser/optimizer result in memory in order
         to use by other session to prevent duplicate execution of parser
and optimizer so therefore get time ?. Because an execution plan is created
before..

Sincenerly

Adnan DURSUN

----- Original Message -----
From: "Tomeh, Husam" <htomeh@firstam.com>
To: "Adnan DURSUN" <a_dursun@hotmail.com>;
<pgsql-performance@postgresql.org>
Sent: Wednesday, October 04, 2006 1:11 AM
Subject: Re: [PERFORM] PostgreSQL Caching



Like many descent RDBMS, Postgresql server allocates its own shared
memory area where data is cached in. When receiving a query request,
Postgres engine checks first its shared memory buffers, if not found,
the engine performs disk I/Os to retrieve data from PostgreSQL data
files and place it in the shared buffer area before serving it back to
the client. Blocks in the shared buffers are shared by other sessions
and can therefore be possibly accessed by other sessions. Postgresql
shared buffers can be allocated by setting the postgresql.conf parameter
namely, shared_buffers.

Sincerely,

--
  Husam

-----Original Message-----
From: pgsql-performance-owner@postgresql.org
[mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Adnan
DURSUN
Sent: Tuesday, October 03, 2006 2:49 PM
To: pgsql-performance@postgresql.org
Subject: [PERFORM] PostgreSQL Caching

        Hi,

    I wonder how PostgreSQL caches the SQL query results. For example ;

        * does postgres cache query result in memory that done by
session A
?
        * does session B use these results ?

Best Regards

Adnan DURSUN


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