#17003: prefetch_related should support foreign keys/one-to-one
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Reporter: lukeplant | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: 1.3
(models, ORM) | Resolution:
Severity: Normal | Triage Stage: Accepted
Keywords: | Needs documentation: 0
Has patch: 0 | Patch needs improvement: 0
Needs tests: 0 | UI/UX: 0
Easy pickings: 0 |
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Comment (by lukeplant):
I've added an implementation that appears to work, and addresses all the
requirements set out above, and has support for `GenericForeignKey`.
The 'API' for finding objects that support prefetching has now increased a
bit:
* we first look on descriptor objects themselves for the
`get_prefetch_query_set` method.
* the return value has expanded a bit:
* to indicate singly related objects, which are a bit treated
differently
* to indicate the cache name, so that singly related objects can be set
up correctly
* to allow a more powerful method of finding the 'join values', the
'attributes' that are returned can be callables - this is needed by
`GenericForeignKey`.
* also, for the singly related case, if the descriptor has the
`get_prefetch_query_set()` method, it also must have an `is_cached()`
method so that we can find out if the objects have already been fetched
(e.g. by select_related).
Docs have also been significantly re-written, since prefetch_related would
now be an alternative to select_related for FK and one-to-one
relationships.
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Ticket URL: <https://code.djangoproject.com/ticket/17003#comment:2>
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