#34207: Incorrect SQL query when adding a ManyToMany related object with a
"through" table prevents adding a new relationship if the new relationship
is identical except for a different value for "through_defaults"
-------------------------------------+-------------------------------------
Reporter: Credentive | Owner: nobody
Type: Bug | Status: closed
Component: Database layer | Version: 4.1
(models, ORM) |
Severity: Normal | Resolution: duplicate
Keywords: ManyToManyField | Triage Stage:
through | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Simon Charette):
* status: new => closed
* resolution: => duplicate
Comment:
`through_defaults` are values that are used to create a missing
relationship between two entities that related to each other through a
many-to-many relationship.
If the relationship already exists between the origin and the destination,
like it's the case when you do `statement.section.add(sect,
through_defaults={"sl_version":new_version})`, then they are ignored as
expected as `ManyToManyField` only supports a single related value between
two entities.
This is reflected in other APIs such as `statement.section.remove` which
doesn't specify through values.
In other words, while `ManyToManyField` supports relationship annotations
these annotations cannot uniquely define the relationship between the
related objects; `ManyToManyField` doesn't support multi-dimensional
relationships.
Duplicate of #33209
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Ticket URL: <https://code.djangoproject.com/ticket/34207#comment:1>
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