fix(queryset): make distinct().count() ignore join-duplicated rows#2255
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fix(queryset): make distinct().count() ignore join-duplicated rows#2255Sanjays2402 wants to merge 1 commit into
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QuerySet.count() always emitted COUNT(*), which counts every row the query produces. When the queryset is distinct() and the filter spans a m2m (or any other row-multiplying join), the returned objects are de-duplicated by the SELECT DISTINCT but the count was not, so count() reported more rows than the queryset actually yields. CountQuery now receives the _distinct flag and counts distinct primary keys instead. Grouped queries keep the existing windowed COUNT(*). Closes tortoise#2178
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Closes #2178
Description
QuerySet.count()always emittedCOUNT(*), which counts every row the query produces.distinct()only setsSELECT DISTINCTon the row query, so when a filter spans an m2m (or any other row-multiplying join) the returned objects were de-duplicated but the count was not.CountQuerynow receives the_distinctflag and counts distinct primary keys; grouped queries keep the existing windowedCOUNT(*).Motivation and Context
Fixes #2178:
Model.filter(m2m_field__name__in=[...]).distinct()returns 1 object but.count()returned 3.How Has This Been Tested?
Added
test_distinct_count_with_m2m_joinintests/test_queryset.py. It fails ondevelop(assert 3 == 1) and passes with the fix. Full suite run on SQLite is unchanged otherwise (1789 -> 1790 passed, same 3 pre-existing environment failures before and after).Checklist: