#28459: Improve performance of QuerySet
-------------------------------------+-------------------------------------
     Reporter:  Sergey Fedoseev      |                    Owner:  nobody
         Type:                       |                   Status:  new
  Cleanup/optimization               |
    Component:  Database layer       |                  Version:  master
  (models, ORM)                      |
     Severity:  Normal               |               Resolution:
     Keywords:                       |             Triage Stage:  Accepted
    Has patch:  1                    |      Needs documentation:  0
  Needs tests:  0                    |  Patch needs improvement:  0
Easy pickings:  0                    |                    UI/UX:  0
-------------------------------------+-------------------------------------

Comment (by Sergey Fedoseev):

 [https://github.com/django/django/pull/9739 PR (Improved performance of
 time difference expressions on MySQL)]

 Before:
 {{{
 %timeit
 bool(TestModel.objects.values_list(models.ExpressionWrapper(models.F('time')
 - models.F('time'), output_field=models.DurationField())))
 35.4 ms ± 901 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
 }}}

 After:
 {{{
 %timeit
 bool(TestModel.objects.values_list(models.ExpressionWrapper(models.F('time')
 - models.F('time'), output_field=models.DurationField())))
 30 ms ± 810 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)
 }}}

-- 
Ticket URL: <https://code.djangoproject.com/ticket/28459#comment:34>
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