From: | Jean-Christian Imbeault <jc(at)mega-bucks(dot)co(dot)jp> |
---|---|
To: | Maksim Likharev <mlikharev(at)aurigin(dot)com> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Duplicate key insert question |
Date: | 2003-07-02 01:10:57 |
Message-ID: | 3F023121.7010209@mega-bucks.co.jp |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general |
Maksim Likharev wrote:
>
> Finding if the duplicate value exists and inserting if not.
Ok, thanks but I think it is still vulnerable to a race condition.
> I do not know how that will work for PG, but in Microsoft SQL Server
> you can do following
> BEGIN TRANSACTION
> UPDATE [val] = [val]
> WHERE ....
> INSERT ...
> COMMIT TRANSACTION
>
> so basically by updating specific row ( let say you have such row )
> in transaction, row/page lock will be held until end of transaction
> and concurrent UPDATE will wait until you are done.
> Kind of semaphore.
Why the UPDATE? And in postgres every query runs in it's own transaction
so no need for the explicit BEGIN / END block.
So can't see how your solution is any better than the previous one :)
Thanks,
Jean-Christian Imbeault
From | Date | Subject | |
---|---|---|---|
Next Message | Martijn van Oosterhout | 2003-07-02 01:16:01 | Re: PSQL NEWBIE - RUNTIME ERROR |
Previous Message | Maksim Likharev | 2003-07-02 01:05:35 | Re: Duplicate key insert question |