#35941: Add composite GenericForeignKey support
-------------------------------------+-------------------------------------
Reporter: Csirmaz Bendegúz | Owner: Csirmaz
| Bendegúz
Type: New feature | Status: assigned
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Changes (by Csirmaz Bendegúz):
* owner: (none) => Csirmaz Bendegúz
* status: new => assigned
Old description:
> This is a follow up to #373 (''CompositePrimaryKey'').
>
> **Proposal:**
>
> My proposal is to implement ''GenericForeignKey'' support with **JSON**.
>
> 1. `object_id` is a `CharField` (or `TextField`)
> 2. ''CompositePrimaryKey'' is stored as a ''JSON array'' in `object_id`
> 3. JOINs can be achieved with JSON functions (varies per db backend)
>
> If anyone is interested, I have a proof of concept available on my
> [https://github.com/csirmazbendeguz/django/pull/9 GitHub] (it's an out of
> sync draft right now, I'll submit a proper PR once composite primary keys
> are merged).
>
> **Risks:**
>
> 1. What if someone is using a JSON array as the primary key (but it's not
> a composite primary key)?
> ''Before deserializing the JSON array, we need to check if the content
> type has a composite primary key or not.''
> 2. What if the db backend doesn't support JSON functions?
> ''All supported databases support JSON functions.''
>
> **Notes:**
>
> Django admin's `LogEntry` has its own implementation of "generic foreign
> keys".
> The approach we take with `GenericForeignKey` should also apply to
> `LogEntry`.
>
> If someone has a better proposal or feedback on my proposal I would be
> happy to hear it.
New description:
This is a follow up to #373 (''CompositePrimaryKey'').
**Proposal:**
My proposal is to implement ''GenericForeignKey'' support with **JSON**.
1. `object_id` is a `CharField` (or `TextField`)
2. ''CompositePrimaryKey'' is stored as a ''JSON array'' in `object_id`
3. JOINs can be achieved with JSON functions (varies per db backend)
**Risks:**
What if someone is using a JSON array as the primary key (but it's not a
composite primary key)?
''Before deserializing the JSON array, we need to check if the content
type has a composite primary key or not.''
What if the db backend doesn't support JSON functions?
''All supported databases support JSON functions.''
**Notes:**
1. JOINs must work with Unicode characters
2. int, date, datetime, uuid, text fields must be supported
3. Django admin's `LogEntry` has its own implementation of "generic
foreign keys". The approach we take with `GenericForeignKey` should also
apply to `LogEntry`.
Any feedback is appreciated!
--
Comment:
Yes, thanks for raising these points Simon!
--
Ticket URL: <https://code.djangoproject.com/ticket/35941#comment:4>
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