#9394: Reverse relation lookups with a multi-table inherited model produces
extraneous queries
---------------------------------------------------+------------------------
Reporter: ikelly | Owner: mtredinnick
Status: assigned | Milestone:
Component: Database layer (models, ORM) | Version: SVN
Resolution: | Keywords:
Stage: Accepted | Has_patch: 0
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Comment (by JasonCreighton):
I'm running into what I think is the same bug. I'm using 1.0.2. Given
these models:
{{{
class Base(models.Model):
base_info = models.CharField(max_length=50)
class Extra(Base):
extra_info = models.CharField(max_length=50)
class ExtraRelatedData(models.Model):
extra = models.ForeignKey(Extra)
related_data = models.CharField(max_length=50)
}}}
And some pre-populated data:
{{{
>>> e = Extra(base_info="foo", extra_info="bar")
>>> e.save()
>>> ed = ExtraRelatedData(extra=e, related_data="quux")
>>> ed.save()
}}}
If I later run:
{{{
>>> e = Extra.objects.get(pk=1)
>>> ExtraRelatedData.objects.filter(extra=e)
[<ExtraRelatedData: ExtraRelatedData object>]
>>> for q in connection.queries: print repr(q)
...
{'time': '0.001', 'sql': u'SELECT
"inheritance_base"."id", "inheritance_base"."base_info",
"inheritance_extra"."base_ptr_id", "inheritance_extra"."extra_info"
FROM "inheritance_extra"
INNER JOIN "inheritance_base" ON ("inheritance_extra"."base_ptr_id" =
"inheritance_base"."id")
WHERE "inheritance_extra"."base_ptr_id" = 1 '}
{'time': '0.000', 'sql': u'SELECT
"inheritance_base"."id", "inheritance_base"."base_info"
FROM "inheritance_base" WHERE "inheritance_base"."id" = 1 '}
{'time': '0.000', 'sql': u'SELECT
"inheritance_extrarelateddata"."id",
"inheritance_extrarelateddata"."extra_id",
"inheritance_extrarelateddata"."related_data"
FROM "inheritance_extrarelateddata"
WHERE "inheritance_extrarelateddata"."extra_id" = 1 LIMIT 21'}
}}}
Even though "e" is already loaded, Django loads it again. (To get the pk?)
I can workaround it like so:
{{{
>>> e = Extra.objects.get(pk=1)
>>> ExtraRelatedData.objects.filter(extra__pk=e.pk)
[<ExtraRelatedData: ExtraRelatedData object>]
>>> for q in connection.queries: print repr(q)
...
{'time': '0.001', 'sql': u'SELECT
"inheritance_base"."id", "inheritance_base"."base_info",
"inheritance_extra"."base_ptr_id", "inheritance_extra"."extra_info"
FROM "inheritance_extra"
INNER JOIN "inheritance_base" ON ("inheritance_extra"."base_ptr_id" =
"inheritance_base"."id")
WHERE "inheritance_extra"."base_ptr_id" = 1 '}
{'time': '0.000', 'sql': u'SELECT
"inheritance_extrarelateddata"."id",
"inheritance_extrarelateddata"."extra_id",
"inheritance_extrarelateddata"."related_data"
FROM "inheritance_extrarelateddata"
WHERE "inheritance_extrarelateddata"."extra_id" = 1 LIMIT 21'}
}}}
[ SQL reformatted slightly ]
It seems completely wrong to me that there's a case where
{{{filter(foo=foo)}}} is not that same as {{{filter(foo__pk=foo.pk)}}}.
So is this the same bug, or should I open a new ticket?
--
Ticket URL: <http://code.djangoproject.com/ticket/9394#comment:5>
Django <http://code.djangoproject.com/>
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