[Django]-IntegrityError: FOREIGN KEY constraint failed in django

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Do DO_NOTHING is typically not a good option since (most) databases will check referential integrity. This means that they guarantee that if a ForeignKey refers (in this case to an Issue), then that means that the table that stores the issues should have a record with the primary key the Return item refers to.

Often DO_NOTHING is used in combination with a certain trigger in the database system (that Django is not aware of).

Typically the most popular choices foron_delete are:

  1. models.CASCADE: in that case it will remove all Returns related to the removed item;
  2. models.PROTECT: in that case it will raise an error to prevent removing the Issue; and
  3. models.SET_NULL: this is done on a NULLable field (so with null=Ture), in which case the impacted Return(s) will set the field to NULL/None.

Another option might be to "soft delete" records, for example with the django-soft-delete package [pypi]. In that case a boolean is added to the Issue that specifies if the item is removed. The package will also transparently filter the objects, such that you only retrieve records that are "alive".

👤willeM_ Van Onsem

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This edge case is not directly relevant for the OP, but may help others that wind up here based on the title:

An IntegrityError: FOREIGN KEY constraint failed will also be raised when trying to delete some object x, if there is a table in your database that Django is unaware of, and this table has a reference to object x.

This can happen, for example, if you remove a model from your code without properly migrating the changes.

As a result, the table remains in the database, but Django does not know anything about it, so, when object x is deleted, Django does not know it should also delete the corresponding row from this "orphaned" table.

👤djvg

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