performance enhancement for testsuite

[Travis Cline <travis.cline@…>]

In my profiling of the test suite get_models appears to be the lowest hanging fruit. Attached is a patch that gives about a 30-35% speed increase for the django testsuite and closer to 40% for Ellington's suite.

[Alex Gaynor]

Though this patch helps testing I've changed the component since the change is actually in DB loading.

[Luke Plant]

(In [11883]) Fixed #12389 - performance enhancement of get_models()

Thanks to Travis Cline for the patch, which gives about 35% speed increase
for the testsuite (with SQLite in-memory DB).

[Luke Plant]

FYI, I tweaked the patch in a few ways, in the spirit of micro-optimisation:

1. Used try/except to avoid doing two dictionary lookups.
2. Moved cache check before self._populate() call.
3. Used a tuple as the cache key, rather than a string, mainly for simplicity and clarity.

Only the last of these had any measurable effect at all, and not much, but they made me feel better :-)

[Alex Gaynor]

Using a tuple helped? That's suprising, CPython dictionaries have some specific optimizations for when strings are used.

[Travis Cline <travis.cline@…>]

I did some timeit benchmarks and it is quicker -- because of the skipping of the creation of the string -- if you already have the string the string lookup is about twice as fast as the tuple lookup (both super quick though).

[Jacob]

Milestone 1.2 deleted