#18279: Django ORM calculation of aggregate position is select queries
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Reporter: deepak@… | Owner: nobody
Type: Bug | Status: new
Component: Database layer (models, ORM) | Version: 1.4
Severity: Normal | Keywords: orm
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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Hello,
I believe I have discovered this bug in django 1.4 ORM. I am not familiar
enough with the ORM to write a patch. Here,
https://github.com/django/django/blob/master/django/db/models/sql/compiler.py#L784
{{{
aggregate_start = len(self.query.extra_select.keys()) +
len(self.query.select)
aggregate_end = aggregate_start + len(self.query.aggregate_select)
row = tuple(row[:aggregate_start]) + tuple([
self.query.resolve_aggregate(value, aggregate,
self.connection)
for (alias, aggregate), value
in zip(self.query.aggregate_select.items(),
row[aggregate_start:aggregate_end])
]) + tuple(row[aggregate_end:])
}}}
I believe aggregate_start should be calculated using the number of non-
deferred fields rather than the length of query.select which is equal to
the all the fields in the model. During some debugging I found that
aggregate_start was being calculated way past the number of elements in
the db returned row. Strangely, the bug has no side-effects because
resolve_aggregate is never called since it operates on an empty list.
Lastly, I think this is a bug but I am not sure why this has no side-
effects.
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Ticket URL: <https://code.djangoproject.com/ticket/18279>
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