#27666: Delay rendering of models in migration operations when possible
-------------------------------------+-------------------------------------
Reporter: Markus Holtermann | Owner: Markus
Type: | Holtermann
Cleanup/optimization | Status: assigned
Component: Migrations | Version: master
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 1 | Needs documentation: 1
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Description changed by Markus Holtermann:
Old description:
> As it turns out, when we delay the rendering of related models up to the
> point where it's necessary (just before RunPython, afaict), we can cut
> down migration time to a quarter and maybe more:
> https://github.com/MarkusH/django/commit/6b8280e0582d778944585e966404252c4994185e#commitcomment-19719252
>
> PR: https://github.com/django/django/pull/7589
>
> Given that 3rd party migration operations may need to enforce model
> rendering like we do for RunPython, we probably need to tread this as a
> backwards incompatible change, I suppose.
>
> {{{#!python
> def database_forwards(self, app_label, schema_editor, from_state,
> to_state):
> if from_state.is_delayed and 'apps' in from_state.__dict__:
> del from_state.__dict__['apps']
> # ...
> }}}
New description:
As it turns out, when we delay the rendering of related models up to the
point where it's necessary (just before RunPython, afaict), we can cut
down migration time to a quarter and maybe more:
https://github.com/MarkusH/django/commit/6b8280e0582d778944585e966404252c4994185e#commitcomment-19719252
PR: https://github.com/django/django/pull/7589
Given that 3rd party migration operations may need to enforce model
rendering like we do for RunPython, we probably need to treat this as a
backwards incompatible change, I suppose.
{{{#!python
def database_forwards(self, app_label, schema_editor, from_state,
to_state):
if from_state.is_delayed and 'apps' in from_state.__dict__:
del from_state.__dict__['apps']
# ...
}}}
--
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Ticket URL: <https://code.djangoproject.com/ticket/27666#comment:3>
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