[Django] #35124: Could bulk_update() aggregate the primary keys in CASE clauses?

[Django]

#35124: Could bulk_update() aggregate the primary keys in CASE clauses?
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Reporter: Vlada | Owner: nobody
Macek |
Type: | Status: new
Cleanup/optimization |
Component: Database | Version: dev
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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I'd like to ask if there's a reason why instead of this

{{{#!python

when_statements = []
for obj in batch_objs:
attr = getattr(obj, field.attname)
if not hasattr(attr, "resolve_expression"):
attr = Value(attr, output_field=field)
when_statements.append(When(pk=obj.pk, then=attr))
}}}

this code isn't used

{{{#!python
when_updates = defaultdict(list)
for obj in batch_objs:
attr = getattr(obj, field.attname)
if not hasattr(attr, "resolve_expression"):
attr = Value(attr, output_field=field)
when_updates[attr].append(obj.pk)
when_statements = [
When(pk__in=pks, then=attr) if len(pks) > 1 else
When(pk=pks[0], then=attr)
for attr, pks in when_updates.items()
]
}}}

in `bulk_update()`. Instead of having `WHEN` for each pk, aggregated `WHEN
("t"."id" IN (14679095, 14679134, 14679335, ...)) THEN ...` would be
produced.

That could massively reduce the query length.

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Ticket URL: <https://code.djangoproject.com/ticket/35124>
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