But what changed in 1.2 vs. 1.1 that caused cloning to become slower? Is it fixes for correctness that were missing?
And if 1.3 is slower than 1.2, why the slow down there?
If the slowness is for a good reason (correctness is about the only one I
can think of that is really valid), then fine. But if the slowdown is just
because it is slower and no one knows why, let's add a performance test for
cloning and make sure Django does not slow down (yeah, this is a hand wave
as performance is a tough thing to maintain, but well worth the effort).
Also, just simply creating a DB object is slower with get_or_create. See
attached script that I used to harp on 1.1 vs. 1.2.5 (slightly modified to
change the names, etc. and requires a proper django view to work). I ran
this against both sqlite and mysql.
-peter
On Mon, Apr 25, 2011 at 9:36 PM, Alexander Schepanovski
<suor....@gmail.com>wrote:
> > Is there a way to identify which queries use cloning?
>
> Every filter, exclude, order_by, select_related and some other calls
> clones it. Slicing too.
>
> > Is there a way rewrite those queries to avoid cloning overhead?
>
> You can rewrite
> qs.filter(a=1).exclude(b=2) as qs.filter(Q(a=1) & !Q(b=2))
> or
> qs = qs.filter(a=1); ...; qs = qs.filter(b=2) as q = {}; q['a'] =
> 1; ...; q['b'] = 2; qs = qs.filter(**q)
>
> But you can't avoid several cloning procs for queryset not modifying
> django or monkey patching.
>
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