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Re: Foreign key order evaluation

From: Gaetano Mendola <mendola(at)bigfoot(dot)com>
To: Michael Fuhr <mike(at)fuhr(dot)org>
Subject: Re: Foreign key order evaluation
Date: 2004-09-28 15:04:07
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-general
Michael Fuhr wrote:
> On Tue, Sep 28, 2004 at 01:30:08PM +0000, Randy Yates wrote:
>>Randy Yates <yates(at)ieee(dot)org> writes:
>>>I'm confused. Where is the lock? Is it on the 1 record in the model table?
> Yes.
>>>If so, why is that record locked? Is it possible in Postgresql to update
>>>the primary key of a record? 
> When you insert a row that has a foreign key reference, PostgreSQL
> does a SELECT FOR UPDATE on the referenced row in the foreign table;
> the lock prevents other transactions from changing the referenced
> row before this transaction completes.  Unfortunately it also
> prevents other transactions from acquiring a lock on the same row,
> so those transactions will block until the transaction holding the
> lock completes.

There are some proposal to have another kind of lock in order to avoid the
above. I hope soon.

Gaetano Mendola

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