Message-ID: <4AB23593.4090906@beecom.ch>
Date: Thu, 17 Sep 2009 15:11:47 +0200
From: Leo Mannhart <leo.mannhart@beecom.ch>
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To: rawi <only4com@web.de>
CC: pgsql-sql@postgresql.org
Subject: Re: Hibernate, web application and only one sequence for all
	primary keys
References: <25490498.post@talk.nabble.com>
In-Reply-To: <25490498.post@talk.nabble.com>
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rawi wrote:
> Hello!
> 
> The subject says it...
> 
> Grails/Hibernate wishes per default one sequence for all tables-PKs and all
> PKs as BigInt.
> 
> What would you think about a database with some tens of tables and
> incidentally low to moderate insert concurrency spread in about the half of
> the tables from at most 10 concurrent users with some 10-20 inserts each?

Caveat: If you use the standard sequence generator in hibernate, it is
not using the postgres-sequence in the "usual" manner. hibernate itself
caches 50 ID's as sequence numbers by default. This means, hibernate
only does a select on the database sequence every 50 numbers. it
multyplies the database sequence by 50 to get the "real" sequence
number. it generates the sequence numbers in blocks of 50 numbers or
according to the sequence cache size.
That said, you would probably not see any performance bottlenecks
because of the sequence number generator in the database, even with
thousands of inserts per second.

> 
> And (for the eventuality of an unexpected need to scale up in the future -
> e.g. integration of multiple databases), from about which size would you
> expect performance penalties due to the sole sequence and the BigInt-PKs?
> 
> I first intend to deploy it on an Intel Pentium 2 Duo (2.5-2.8GHz) with 3 GB
> RAM and SATA hard disk under Ubuntu Server.
> 
> Thank you very much in advance!
> Regards
> Rawi

cheers, leo