#12132: possibly unneccessary unique_check for primary key fields is models
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Reporter: Mark | Owner: nobody
Status: new | Milestone:
Component: Database layer (models, ORM) | Version:
soc2009/model-validation
Keywords: model-validation validation unique | Stage: Unreviewed
Has_patch: 1 |
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Every time a clean() method of the model instance is run,
validate_unique() is performed. It seems, that _get_unique_checks doesn't
get into account, that the primary key doesn't need such a check. The sql
that is run during the check is meaningless (it is only meaningless if we
are checking a primary key field):
{{{
SELECT (1) AS "a" FROM "test_models_testmodel" WHERE
("test_models_testmodel"."id" = 1 AND NOT ("test_models_testmodel"."id" =
1 ))
}}}
This results in unnecessary database hits and (possible) performance
degradation. I have put together a simple test rack, so that the effect
can be easily observed. It's not a real test case, but I really hope, that
it will be sufficient.
If I understand correctly, it can be easily fixed, by checking if a field
is a primary key inside the _get_unique_checks model instance method
(patch included).
--
Ticket URL: <http://code.djangoproject.com/ticket/12132>
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