Message-ID: <4C3867DD.1020004@2ndquadrant.com>
Date: Sat, 10 Jul 2010 13:30:21 +0100
From: Greg Smith <greg@2ndquadrant.com>
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To: Jesper Krogh <jesper@krogh.cc>
CC: Matthew Wakeling <matthew@flymine.org>,
	Kevin Grittner <Kevin.Grittner@wicourts.gov>,
	Brad Nicholson <bnichols@ca.afilias.info>,
	pgsql-performance@postgresql.org, Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: Need help in performance tuning.
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Jesper Krogh wrote:
> I dont think a build-in connection-poller (or similiar) would in any
> way limit the actions and abillities of an external one?

Two problems to recognize.  First is that building something in has the 
potential to significantly limit use and therefore advancement of work 
on external pools, because of the "let's use the built in one instead of 
installing something extra" mentality.  I'd rather have a great external 
project (which is what we have with pgBouncer) than a mediocre built-in 
one that becomes the preferred way just by nature of being in the core.  
If work on a core pooler was started right now, it would be years before 
that reached feature/performance parity, and during that time its 
existence would be a net loss compared to the current status quo for 
many who used it.

The second problem is the limited amount of resources to work on 
improvements to PostgreSQL.  If you want to improve the reach of 
PostgreSQL, I consider projects like materialized views and easy 
built-in partitioning to be orders of magnitude more useful things to 
work on than the marginal benefit of merging the features of the 
external pool software inside the database.  I consider the whole topic 
a bit of a distraction compared to instead working on *any* of the 
highly rated ideas at http://postgresql.uservoice.com/forums/21853-general

As a random technical note, I would recommend that anyone who is 
thinking about a pooler in core take a look at how pgBouncer uses 
libevent to respond to requests, a design model inspired by that of 
memcached.  I haven't looked at it deeply yet, but my gut guess is that 
this proven successful model would be hard to graft on top of the 
existing PostgreSQL process design, and doing anything but that is 
unlikely to perform as well.

-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com   www.2ndQuadrant.us