#36987: UUIDField.get_db_prep_value does not observe prepared argument
-------------------------------------+-------------------------------------
Reporter: Jacob Walls | Owner: Jacob
Type: | Walls
Cleanup/optimization | Status: assigned
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Description changed by Jacob Walls:
Old description:
> The
> [https://docs.djangoproject.com/en/6.0/ref/models/fields/#django.db.models.Field.get_db_prep_value
> doc'd "default" pattern] for fields is for `get_db_prep_value()` to call
> the `get_prep_value()` method if `prepared` is False. The idea being, I
> assume, to avoid wasted computation if the value is already
> `prepared=True`.
>
> `UUIDField` doesn't follow this pattern, causing two extra calls to
> `isinstance(val, UUID)` per value, which can add up for a large bag of
> values, e.g. a `prefetch_related()` call.
>
> Here is a [https://dryorm.xterm.info/uuidfield-get-db-prep-value fiddle]
> on DryORM with my fix branch checked out. Re-run the fiddle against main
> and notice 4 fewer calls to isinstance (2 * n objects).
>
> Discovered while reviewing the profile in a
> [https://github.com/django/django/pull/20779/changes micro-optimization
> PR]
> ----
>
> I acknowledge there is some exploratory effort toward removing this
> argument in a [https://github.com/django/django/pull/19051 draft PR].
New description:
The
[https://docs.djangoproject.com/en/6.0/ref/models/fields/#django.db.models.Field.get_db_prep_value
doc'd "default" pattern] for fields is for `get_db_prep_value()` to call
the `get_prep_value()` method if `prepared` is False. The idea being, I
assume, to avoid wasted computation if the value is already
`prepared=True`.
`UUIDField` doesn't follow this pattern, causing two extra calls to
`isinstance(val, UUID)` per value, which can add up for a large bag of
values, e.g. a `prefetch_related()` call.
Here is a [https://dryorm.xterm.info/uuidfield-get-db-prep-value fiddle]
on DryORM with my fix branch checked out. Re-run the fiddle against main
and notice 4 more calls to isinstance (2 * n objects).
Discovered while reviewing the profile in a
[https://github.com/django/django/pull/20779/changes micro-optimization
PR]
----
I acknowledge there is some exploratory effort toward removing this
argument in a [https://github.com/django/django/pull/19051 draft PR].
--
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Ticket URL: <https://code.djangoproject.com/ticket/36987#comment:2>
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