#20880: Split clone() to clone() and pre_next_op()
-------------------------------------+-------------------------------------
Reporter: akaariai | Owner: nobody
Type: | Status: new
Cleanup/optimization | Version: master
Component: Database layer | Resolution:
(models, ORM) | Triage Stage: Accepted
Severity: Normal | Needs documentation: 0
Keywords: | Patch needs improvement: 0
Has patch: 0 | UI/UX: 0
Needs tests: 0 |
Easy pickings: 0 |
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Comment (by akaariai):
I updated (force-pushed) to
https://github.com/akaariai/django/tree/splitted_clone. The patch is
pretty good (cleanup needed), and shows promising results for model saving
and some other queryset operations:
{{{
Running 'model_save_existing' benchmark ...
Min: 0.014001 -> 0.010278: 1.3622x faster
Avg: 0.014304 -> 0.010394: 1.3763x faster
Significant (t=37.226713)
Running 'model_save_new' benchmark ...
Min: 0.013848 -> 0.010196: 1.3582x faster
Avg: 0.014079 -> 0.010408: 1.3527x faster
Significant (t=20.503974)
Running 'query_get' benchmark ...
Min: 0.027801 -> 0.023326: 1.1918x faster
Avg: 0.028116 -> 0.023599: 1.1914x faster
Significant (t=31.307197)
}}}
For qs_filter_chaining (~5 .filter() calls) using inplace results in
speedup of:
{{{
Running 'qs_filter_chaining_inplace' benchmark ...
Min: 0.000892 -> 0.000553: 1.6132x faster
Avg: 0.000937 -> 0.000571: 1.6424x faster
Significant (t=16.654697)
}}}
This is by no means complex query, yet it shows promising results.
So, it is worth considering if .inplace() should be public API. If so,
then it would make sense to guard against using stale versions of the
queryset. This is doable by cloning the outer QuerySet. Skipping cloning
of the internal Query, should give most of the speedup.
Another consideration is that if the ._clone() should be renamed to
._copy() or something. The patched version ._clone() does subtly different
thing than the old version, so this might cause some grey hairs for those
who use that internal API.
--
Ticket URL: <https://code.djangoproject.com/ticket/20880#comment:2>
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