Re: updating unique columns - Mailing list pgsql-bugs

From Greg Sabino Mullane
Subject Re: updating unique columns
Date
Msg-id f42c4766698d5af47343e397acdd83e9@biglumber.com
Whole thread Raw
In response to  (claus.pruefer@webcodex.de)
List pgsql-bugs
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1


| UPDATE
| orderby SET orderby = orderby +10
| WHERE groupid = 1;
| -> FAILS because of UNIQUE INDEX

One workaround is to do it in two steps, assuming that
orderby is > 0 for all rows you are changing:

BEGIN;
UPDATE mytable SET orderby = -orderby WHERE groupid = 1;
UPDATE mytable SET orderby = -orderby+10 WHERE groupid = 1;
COMMIT;


| UPDATE
| orderby SET orderby = orderby +10
| WHERE groupid IN
| ( SELECT groupid
|  FROM TABLE WHERE group_id = 1
|  ORDER BY orderby DESC )

No idea what you are trying to do here: try posting the actual SQL
used. However, an ORDER BY has no meaning inside of a subselect
passed to IN, as IN treats the list as bag of values, and does not
care about the internal order.

- --
Greg Sabino Mullane greg@turnstep.com
PGP Key: 0x14964AC8 200606011030
http://biglumber.com/x/web?pk=2529DF6AB8F79407E94445B4BC9B906714964AC8

-----BEGIN PGP SIGNATURE-----

iD8DBQFEfvpFvJuQZxSWSsgRAjQlAKDTNIpwbSEk0gcQp2pI7LokG+qwWgCgt/b6
/7ZWYDb4gufE4b0zCHyFZgg=
=4LQ8
-----END PGP SIGNATURE-----

pgsql-bugs by date:

Previous
From: Alvaro Herrera
Date:
Subject: Re:
Next
From: "Qingqing Zhou"
Date:
Subject: Re: statement stuck when the connection grew up to 45 or more