Simon Charette 0701bb8e1f Fixed #33928 -- Avoided unnecessary queries when cascade updating. ... Models that use SET, SET_NULL, and SET_DEFAULT as on_delete handler don't have to fetch objects for the sole purpose of passing them back to a follow up UPDATE query filtered by the retrieved objects primary key. This was achieved by flagging SET handlers as _lazy_ and having the collector logic defer object collections until the last minute. This should ensure that the rare cases where custom on_delete handlers are defined remain uncalled when when dealing with an empty collection of instances. This reduces the number queries required to apply SET handlers from 2 to 1 where the remaining UPDATE use the same predicate as the non removed SELECT query. In a lot of ways this is similar to the fast-delete optimization that was added in #18676 but for updates this time. The conditions only happen to be simpler in this case because SET handlers are always terminal. They never cascade to more deletes that can be combined. Thanks Renan GEHAN for the report.		2022-08-27 14:25:55 +02:00
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__init__.py	Removed unneeded imports in tests's __init__.py and unified them.	2013-09-09 23:01:07 +02:00
models.py	Fixed #33928 -- Avoided unnecessary queries when cascade updating.	2022-08-27 14:25:55 +02:00
tests.py	Fixed #33928 -- Avoided unnecessary queries when cascade updating.	2022-08-27 14:25:55 +02:00