Re: SQL design pattern for a delta trigger? - Mailing list pgsql-general

From Vivek Khera
Subject Re: SQL design pattern for a delta trigger?
Date
Msg-id FF08171D-0F1F-4AA7-91F4-ACE7D345D591@kcilink.com
Whole thread Raw
In response to Re: SQL design pattern for a delta trigger?  (Colin Wetherbee <cww@denterprises.org>)
Responses Re: SQL design pattern for a delta trigger?
Re: SQL design pattern for a delta trigger?
List pgsql-general
On Dec 10, 2007, at 5:04 PM, Colin Wetherbee wrote:

> For what it's worth, the real algorithm would be as follows.  I
> hadn't had enough coffee yet, and I forgot the UPDATE bit.
>
> IF
>  (a query matching your old data returns rows)
> THEN
>  UPDATE with your new data
> ELSE
>  INSERT your new data

Still exists race condition.  Your race comes from testing existence,
then creating/modifying data afterwards.  You need to make the test/
set atomic else you have race.


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