From: | Jack Christensen <jackc(at)hylesanderson(dot)edu> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: WITH x AS (...) and visibility in UPDATE |
Date: | 2011-07-27 23:10:08 |
Message-ID: | 4E309AD0.2060808@hylesanderson.edu |
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Lists: | pgsql-general |
On 7/27/2011 4:22 PM, Peter V wrote:
> I want to apply updates on a copy of a row, instead on the row itself.
> The queries are above were simplied to demonstrate the problem.
> So basically I want to do:
>
> 1) create the copy of the row and return the identifier
> 2) apply updates on the new row identified by the identifier returned in step 1
>
> If possible, I want to write this in a single command, to avoid overhead and mistakes.
>
> I tried writing a rewrite rule or before trigger, but it becomes quickly a mess to avoid infinite loops.
>
> Any ideas are welcome. Thanks.
>
Maybe I'm totally missing something, but why insert a copy and then
update instead of directly insert a mutated copy?
Something like:
INSERT INTO t (foo, bar) SELECT 'my new foo', t.bar FROM t WHERE id=123;
Wouldn't the above construction let you make a new row with some new
values and some copied values?
--
Jack Christensen
jackc(at)hylesanderson(dot)edu
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