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Message-ID: <4AB2504F.1010405@gmail.com>
Date: Thu, 17 Sep 2009 09:05:51 -0600
From: Rob Sargent <robjsargent@gmail.com>
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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> <4AB23593.4090906@beecom.ch>
	<25491924.post@talk.nabble.com>
In-Reply-To: <25491924.post@talk.nabble.com>
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Above all, do not fret about whether or not it is "cool to lose" some 
ids.  There are plenty of integers; the ids need not be consecutive.  I 
don't think Grails requires a single sequence source and I know 
hibernate does not.  Hibernate will allow one to inject any sequence/id 
generator you wish to use (including one which generates UUIDs).

rawi wrote:
> Leo Mannhart wrote:
>   
>> 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.
>>
>>     
>
> Hi Leo, thank you for the explanation!
>
> I don't know if it is that cool to lose up to 50 IDs on each session-end of
> Hibernate...
> And what do you suppose it would happen, if I set the cache size of
> Hibernate's own sequence (after generation) by hand to 1 instead of 50? I
> wouldn't need tausends of inserts per second...
>
> Kind regards, Rawi
>
>