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Refs #34964 -- Doc'd that Q expression order is preserved.

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David Sanders 2023-11-16 21:56:36 +11:00 committed by Mariusz Felisiak
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commit 7714ccfeae
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docs/ref/models/constraints.txt
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@ -119,6 +119,18 @@ specifies the check you want the constraint to enforce.
For example, ``CheckConstraint(check=Q(age__gte=18), name='age_gte_18')`` For example, ``CheckConstraint(check=Q(age__gte=18), name='age_gte_18')``
ensures the age field is never less than 18. ensures the age field is never less than 18.
.. admonition:: Expression order
``Q`` argument order is not necessarily preserved, however the order of
``Q`` expressions themselves are preserved. This may be important for
databases that preserve check constraint expression order for performance
reasons. For example, use the following format if order matters::
CheckConstraint(
check=Q(age__gte=18) & Q(expensive_check=condition),
name="age_gte_18_and_others",
)
.. admonition:: Oracle .. admonition:: Oracle
Checks with nullable fields on Oracle must include a condition allowing for Checks with nullable fields on Oracle must include a condition allowing for