sqlmigrate is slow

[TorstenRottmann]

When requesting an sqlmigrate (or when do a test or migrate also), it takes a very long time to compute the sql for a particular app migration. This app has some 78 models and is highly interconnected with ForeignKeys (100+).

I ran the sqlmigrate through the profiler an got these results:

         74628418 function calls (74229555 primitive calls) in 3653.843 seconds

   Ordered by: internal time

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        4 3519.805  879.951 3519.805  879.951 {method 'write' of 'file' objects}
   552977   18.609    0.000   29.893    0.000 __init__.py:292(deconstruct)
    40096   14.244    0.000   20.051    0.001 related.py:276(swappable_setting)
   318698   11.924    0.000   21.114    0.000 __init__.py:1011(__init__)
   575182    9.569    0.000   12.634    0.000 __init__.py:123(__init__)
   571729    7.336    0.000   97.027    0.000 state.py:277(construct_fields)
16773896/16722010    6.750    0.000    6.790    0.000 {getattr}
    85138    2.849    0.000    4.883    0.000 __init__.py:1092(__init__)
553122/553106    2.546    0.000    6.503    0.000 {__import__}
637429/318719    1.916    0.000    2.146    0.000 deconstruct.py:15(__new__)
  3236790    1.912    0.000    1.912    0.000 {method 'startswith' of 'unicode' objects}
3881367/3881365    1.891    0.000    4.462    0.000 {isinstance}
  5915601    1.566    0.000    1.841    0.000 options.py:283(_swapped)
    43868    1.525    0.000    1.525    0.000 base.py:33(subclass_exception)
   901715    1.508    0.000    2.571    0.000 abc.py:128(__instancecheck__)
21946/19820    1.486    0.000   24.646    0.001 base.py:61(__new__)
...

Waiting more than a minute for a test to start is very annoying ...