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Re: connections

From: "Dave Page" <dpage(at)pgadmin(dot)org>
To: "Roberts, Jon" <Jon(dot)Roberts(at)asurion(dot)com>
Cc: pgadmin-hackers <pgadmin-hackers(at)postgresql(dot)org>
Subject: Re: connections
Date: 2008-04-21 06:27:40
Message-ID: 937d27e10804202327w42e681abodc6557d50f0f07b7@mail.gmail.com (view raw or flat)
Thread:
Lists: pgadmin-hackers
On Sun, Apr 20, 2008 at 6:00 PM, Dave Page <dpage(at)pgadmin(dot)org> wrote:
> On Fri, Apr 18, 2008 at 7:30 PM, Roberts, Jon <Jon(dot)Roberts(at)asurion(dot)com> wrote:
>
> I'm awaiting confirmation from the lead architect, but I believe that
> a single connection from pgAdmin will result in 1 connection to each
> node in the cluster in GridSQL. However I believe there is also a
> certain amount of pooling going on so I don't believe it's such a
> problem. Besides.... that may be 16 connections in a 16 node system,
> but each of those is a complete PostgreSQL/EnterpriseDB server capable
> of handling as many connections as it could if it were a standalone
> server (which could be hundreds or thousands), so it's no more an
> issue than if you had a single server.

The word from the GridSQL guru is:

I am not sure I understand why he has so many connections because each
segment should be on a different host. Maybe they have something set
up where there are multiple logical nodes (er, segments) running on a
single postmaster instance.

Maybe that further explodes if each segment creates a connection to
every other one and persists it.

In GridSQL, we have a pool of connections that are used, starting with
5 for each underlying node. These are shared amongst the users, unless
somethings stateful happens in which case the underlying connection
needs to become persistent for a user session. We also have an extra
connection for the metadata database, and some vestiges of old code
for a pool of "coordinator" connections, but they are not used for
most queries.

Anyway, the bottom line is, GridSQL will not consume as many
connections as in the Greenplum case.

-- 
Dave Page
EnterpriseDB UK: http://www.enterprisedb.com

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