#35241: Cache Model._meta.get_parent_list()
-------------------------------------+-------------------------------------
     Reporter:  Adam Johnson         |                    Owner:  Adam
         Type:                       |  Johnson
  Cleanup/optimization               |                   Status:  assigned
    Component:  Database layer       |                  Version:  dev
  (models, ORM)                      |
     Severity:  Normal               |               Resolution:
     Keywords:                       |             Triage Stage:  Accepted
    Has patch:  1                    |      Needs documentation:  0
  Needs tests:  0                    |  Patch needs improvement:  1
Easy pickings:  0                    |                    UI/UX:  0
-------------------------------------+-------------------------------------

Old description:

> Another candidate for caching, like #35230 and #35232, following the same
> system check profiling.
>
> `Model._meta.get_parent_list()` computes the flattened list of ancestor
> models by MRO. This list is immutable, deterministic, and recursively
> constructed through the inheritance hierarchy. These properties make it a
> prime candidate for caching.
>
> I found this method was taking ~1% of the total runtime for system checks
> on a project with 118 models. After adding caching, it’s reduced to a
> negligible amount.
>
> `get_parent_list()` is called in many other code paths, so caching will
> help all of those too.

New description:

 Another candidate for caching, like #35230 and #35232, following the same
 system check profiling.

 `Model._meta.get_parent_list()` computes the flattened list of ancestor
 models by MRO. This list is immutable, deterministic, and recursively
 constructed through the inheritance hierarchy. These properties make it a
 prime candidate for caching.

 I found this method was taking ~1% (0.39ms) of the total runtime for
 system checks on a project with 118 models. After adding caching, it’s
 reduced to a negligible amount (<0.01ms).

 `get_parent_list()` is called in many other code paths, so caching will
 help all of those too.

--
Comment (by Adam Johnson):

 I added concrete numbers to the description.
-- 
Ticket URL: <https://code.djangoproject.com/ticket/35241#comment:3>
Django <https://code.djangoproject.com/>
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