Date: Tue, 28 Mar 2006 23:18:39 +0200
To: Marcos <mjs_ops@gmx.net>
Subject: Re: Decide between Postgresql and Mysql (help of
References: <1143559902.1241.16.camel@servidor>
	<1143572392.3625.79.camel@state.g2switchworks.com>
	<1143564928.1241.28.camel@servidor>
Cc: pgsql-performance@postgresql.org
From: PFC <lists@peufeu.com>
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>> So, what exactly are you planning on doing?
>
> The application will be a chat for web, the chats will be stored in the
> server. In a determined interval of time... more or less 2 seconds, the
> application will be looking for new messages.
>
> I believe that it will make many accesses. The write in disc will be
> constant.

	Ah, cool. That's exactly what a database is not designed for xD

	Try this, I coded this in about 1 hour as a joke last week.
	http://peufeu.com/demos/xhchat/
	It works in firefox and opera, uses xmlhttprequest, and the messages are  
stored in a dbm database.

	We have also coded a real HTTP chat. I'll briefly expose the details  
on-list, but if you want the gory stuff, ask privately.

	There is a Postgres database for users, authentication, chatrooms and  
stuff. This database can be modified by a full-blown web application.
	Of course, messages are not stored in the database. It would be suicidal  
performance-wise to do so.

	An asynchronous HTTP server, using select() (lighttpd style) is coded in  
Python. It is very special-purpose server. It keeps an open connection  
with the client (browser) and sends messages as they arrive in the  
chatroom, with no delay. The connection is interrupted only when the  
client submits a new message via a form, but this is not mandatory.

	My memories are a bit old, but we benchmarked it at about 4000  
messages/second on a low-end server (athlon something). Concurrent  
connections are unlimited. Disk I/O is zero. I like it.
	If you store messages in the database, you can hope to be about 10-50  
times slower.