Re: PostgreSQL clustering VS MySQL clustering - Mailing list pgsql-performance

From Josh Berkus
Subject Re: PostgreSQL clustering VS MySQL clustering
Date
Msg-id 200501231442.52830.josh@agliodbs.com
Whole thread Raw
In response to Re: PostgreSQL clustering VS MySQL clustering  (Tatsuo Ishii <t-ishii@sra.co.jp>)
Responses Re: PostgreSQL clustering VS MySQL clustering
List pgsql-performance
Tatsuo,

> I'm not clear what "pgPool only needs to monitor "update switching" by
>
> *connection* not by *table*" means. In your example:
> > (1) 00:00 User A updates "My Profile"
> > (2) 00:01 "My Profile" UPDATE finishes executing.
> > (3) 00:02  User A sees "My Profile" re-displayed
> > (6) 00:04  "My Profile":UserA cascades to the last Slave server
>
> I think (2) and (3) are on different connections, thus pgpool cannot
> judge if SELECT in (3) should go only to the master or not.
>
> To solve the problem you need to make pgpool understand "web sessions"
> not "database connections" and it seems impossible for pgpool to
> understand "sessions".

Depends on your connection pooling software, I suppose.  Most connection
pooling software only returns connections to the pool after a user has been
inactive for some period ... generally more than 3 seconds.  So connection
continuity could be trusted.

--
Josh Berkus
Aglio Database Solutions
San Francisco

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