id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
22608	Migrations optimizer slow (due to double working?)	David S	nobody	"`makemigrations` is currently fairly conservative with splitting operations into separate migrations, e.g. when there are fk dependencies. after manually merging some of these i noticed a significant speedup, which surprised andrewgodwin

did some basic profiling and it looks like many smaller migration need to re-do some work. will try to look more into this, but wanted to raise a ticket to track

separate:
38 migrations over 9 apps (3, 14, 6, 3, 1, 1, 5, 2, 3)

profiling `./manage.py test app1` around `executor.migrate(targets, plan, fake=options.get(""fake"", False))`

{{{
         17353606 function calls (17308702 primitive calls) in 39.818 seconds

   Ordered by: internal time
   List reduced from 505 to 10 due to restriction <10>

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
   152757    7.436    0.000   12.352    0.000 /Users/david/dev/django_source/django/db/models/fields/__init__.py:290(deconstruct)
   155191    3.989    0.000    5.518    0.000 /Users/david/dev/django_source/django/db/models/fields/__init__.py:121(__init__)
    22617    3.125    0.000    4.428    0.000 /Users/david/dev/django_source/django/db/models/fields/related.py:276(swappable_setting)
4561050/4537097    2.817    0.000    2.843    0.000 {getattr}
      419    2.477    0.006    2.478    0.006 {method 'execute' of 'psycopg2._psycopg.cursor' objects}
    16993    1.477    0.000   27.452    0.002 /Users/david/dev/django_source/django/db/migrations/state.py:229(clone)
    12854    0.833    0.000    1.117    0.000 /usr/local/Cellar/python/2.7.3/Frameworks/Python.framework/Versions/2.7/lib/python2.7/collections.py:37(__init__)
852604/852602    0.796    0.000    1.643    0.000 {isinstance}
  1558116    0.706    0.000    0.882    0.000 /Users/david/dev/django_source/django/db/models/options.py:282(_swapped)
  3124169    0.655    0.000    0.666    0.000 {method 'get' of 'dict' objects}
}}}

manually merged into 1 migration per app:

{{{
         3650282 function calls (3640151 primitive calls) in 9.895 seconds

   Ordered by: internal time
   List reduced from 495 to 10 due to restriction <10>

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
      321    0.959    0.003    0.959    0.003 {method 'execute' of 'psycopg2._psycopg.cursor' objects}
    19363    0.898    0.000    1.646    0.000 /Users/david/dev/django_source/django/db/models/fields/__init__.py:290(deconstruct)
    20870    0.648    0.000    0.874    0.000 /Users/david/dev/django_source/django/db/models/fields/__init__.py:121(__init__)
     3236    0.432    0.000    0.656    0.000 /Users/david/dev/django_source/django/db/models/fields/related.py:276(swappable_setting)
642018/638002    0.427    0.000    0.432    0.000 {getattr}
    32654    0.331    0.000    0.331    0.000 {method 'items' of 'dict' objects}
     5662    0.286    0.000    0.286    0.000 /Users/david/dev/django_source/django/db/models/base.py:34(subclass_exception)
     6823    0.232    0.000    0.232    0.000 /Users/david/dev/django_source/django/utils/functional.py:15(curry)
   180384    0.230    0.000    0.230    0.000 {hasattr}
     3673    0.225    0.000    0.511    0.000 /Users/david/dev/django_source/django/db/models/fields/related.py:1584(__init__)
}}}"	Cleanup/optimization	closed	Migrations	dev	Normal	duplicate		Andrew Godwin paul.collins.iii@… michaelvantellingen@…	Accepted	0	0	0	0	0	0