Message-ID: <4B69934E.6060606@beecom.ch>
Date: Wed, 03 Feb 2010 16:16:30 +0100
From: Leo Mannhart <leo.mannhart@beecom.ch>
User-Agent: Thunderbird 2.0.0.23 (X11/20090817)
MIME-Version: 1.0
To: wyx6fox@sina.com
CC: pgsql-performance@postgresql.org
Subject: Re: some problems when i use postgresql 8.4.2 in my projects
 .
References: <20100203022830.2A375358C60@mail175-236.sinamail.sina.com.cn>
In-Reply-To: <20100203022830.2A375358C60@mail175-236.sinamail.sina.com.cn>
Content-Type: text/plain; charset=x-gbk
Content-Transfer-Encoding: 7bit

wyx6fox@sina.com wrote:
> after shaming , I think i should pick out some my points:
>  the unique constraints actualy kill concurrency write transaction when
> concurrency insert violate the unique constraints , they block each
> other , i test this in oracle10g, has the same behavour. I think this
> may be reasonable because the uqniue check must be  the seriazable check .
> for resolve this problem , i do the unique check in application as
> possible , but in big concurrency env , this is not good way .
> 

How can you enforce uniqueness in the application? If you implement it
correctly, you need considerably longer than letting it do PostgreSQL.
Even if you use some kind of magic, I could not imagine, how you can
implement a unique constraint in the application and gaurantee
uniqueness while at the same time be faster than the RDBMS.

Leo