id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
34580	Performance regession in SQLCompiler	David Smith	David Smith	"Looking at the Django's [https://django.github.io/django-asv/ ASV benchmarks ] the [https://django.github.io/django-asv/#query_benchmarks.query_count.benchmark.QueryCount.time_query_count query count ] and [https://django.github.io/django-asv/#query_benchmarks.query_aggregate.benchmark.QueryAggr.time_aggregate aggregate ] benchmarks show performance regressions.

Rough orders of magnitude are 
Query Count 1.257ms -> 1.849ms 47% Increase
Aggregate 0.882ms -> 1.238ms 40% Increase
 
I managed to bisect the regression to this commit https://github.com/django/django/commit/278881e3 | 
278881e37619278789942513916acafaa88d26f3"	Cleanup/optimization	closed	Database layer (models, ORM)	4.2	Release blocker	fixed		Simon Charette	Ready for checkin	1	0	0	0	0	0