diff options
Diffstat (limited to 'docs/ref/models/instances.txt')
| -rw-r--r-- | docs/ref/models/instances.txt | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/docs/ref/models/instances.txt b/docs/ref/models/instances.txt index d03b05577c..346ae55130 100644 --- a/docs/ref/models/instances.txt +++ b/docs/ref/models/instances.txt @@ -541,7 +541,8 @@ You may have noticed Django database objects use the same ``save()`` method for creating and changing objects. Django abstracts the need to use ``INSERT`` or ``UPDATE`` SQL statements. Specifically, when you call ``save()`` and the object's primary key attribute does **not** define a -:attr:`~django.db.models.Field.default`, Django follows this algorithm: +:attr:`~django.db.models.Field.default` or +:attr:`~django.db.models.Field.db_default`, Django follows this algorithm: * If the object's primary key attribute is set to a value that evaluates to ``True`` (i.e., a value other than ``None`` or the empty string), Django @@ -551,9 +552,10 @@ object's primary key attribute does **not** define a exist in the database), Django executes an ``INSERT``. If the object's primary key attribute defines a -:attr:`~django.db.models.Field.default` then Django executes an ``UPDATE`` if -it is an existing model instance and primary key is set to a value that exists -in the database. Otherwise, Django executes an ``INSERT``. +:attr:`~django.db.models.Field.default` or +:attr:`~django.db.models.Field.db_default` then Django executes an ``UPDATE`` +if it is an existing model instance and primary key is set to a value that +exists in the database. Otherwise, Django executes an ``INSERT``. The one gotcha here is that you should be careful not to specify a primary-key value explicitly when saving new objects, if you cannot guarantee the @@ -570,6 +572,10 @@ which returns ``NULL``. In such cases it is possible to revert to the old algorithm by setting the :attr:`~django.db.models.Options.select_on_save` option to ``True``. +.. versionchanged:: 5.0 + + The ``Field.db_default`` parameter was added. + .. _ref-models-force-insert: Forcing an INSERT or UPDATE |