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Diffstat (limited to 'docs/ref/models/expressions.txt')
| -rw-r--r-- | docs/ref/models/expressions.txt | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/docs/ref/models/expressions.txt b/docs/ref/models/expressions.txt index b6512bff72..8879ee1a8f 100644 --- a/docs/ref/models/expressions.txt +++ b/docs/ref/models/expressions.txt @@ -37,6 +37,12 @@ determine the result's field type, such as complex expressions that mix field types. For example, adding a ``DecimalField()`` and a ``FloatField()`` requires an output field, like ``output_field=FloatField()``. +``output_field`` also allows using custom fields that perform type conversions +outside a specific model field context. For example, if you frequently need to +perform date arithmetic with ``timedelta``, you can create a custom field that +handles the conversion, ensuring consistent results across databases. See +:doc:`/howto/custom-model-fields`. + Some examples ============= @@ -559,6 +565,12 @@ available on other expressions. ``ExpressionWrapper`` is necessary when using arithmetic on ``F()`` expressions with different types as described in :ref:`using-f-with-annotations`. +.. admonition:: Database casting not performed + + ``ExpressionWrapper`` only sets the output field for the ORM and does not + perform any database-level casting. To ensure a specific type is returned + from the database, use :class:`~django.db.models.functions.Cast` instead. + Conditional expressions ----------------------- |