Peter Melvyn skrev:
> Hi all,
>
> if I'm not mistaken, if I have a model with unique constraint
> 'unique_together', Django does not support composite index of related
> columns, i.e.
>
> class AModel (models.Model):
> col_a = models.CharField(maxlength=20, db_index=True)
> col_b = models.CharField(maxlength=20, db_index=True)
> class Meta:
> unique_together = (('col_a','col_b'),)
>
> generates SQL commands:
>
> CREATE TABLE `xxx_amodel` (
> `id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
> `col_a` varchar(20) NOT NULL,
> `col_b` varchar(20) NOT NULL,
> UNIQUE (`col_a`, `col_b`)
> );
> CREATE INDEX `xxx_amodel_col_a` ON `wss_amodel` (`col_a`);
> CREATE INDEX `xxx_amodel_col_b` ON `wss_amodel` (`col_b`);
>
>
> Should not be there another meta command, e.g.
>
> indexed_together = (('col_a','col_b'),)
>
> producing index
>
> CREATE INDEX `xxx_amodel_col_a_col_b`
> ON `wss_amodel` (`col_a`,`col_b`);
Postgresql will implicitly generate this index when it encounters the
UNIQUE constraint. My guess is that other backends will do the same.
A more interesting case is when you want to create multifield indices
which aren't unique. Your syntax could be used for this.
Nis
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