#13844: Errors when using character fields for aggregation
---------------------------------------------------+------------------------
Reporter: [email protected] | Owner: nobody
Status: new | Milestone:
Component: Database layer (models, ORM) | Version: 1.2
Resolution: | Keywords:
Stage: Accepted | Has_patch: 1
Needs_docs: 0 | Needs_tests: 0
Needs_better_patch: 0 |
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Changes (by chronos):
* cc: [email protected] (added)
* has_patch: 0 => 1
Comment:
I'm the guy at IRC. The proposed fix already works for me. I having
troubles in get Max from a charfield.
Given model:
{{{
class Link_A(models.Model):
link = models.CharField(max_length=500)
short_link = models.CharField(max_length=50)
}}}
I get following error when try to get Max of short_link:
{{{
In [5]: Link_A.objects.all().aggregate(Max('short_link'))
---------------------------------------------------------------------------
ValueError Traceback (most recent call
last)
/home/felipe/projects/testproject/<ipython console> in <module>()
/home/felipe/.py/2.6/lib/python2.6/site-
packages/django/db/models/query.pyc in aggregate(self, *args, **kwargs)
311 is_summary=True)
312
--> 313 return query.get_aggregation(using=self.db)
314
315 def count(self):
/home/felipe/.py/2.6/lib/python2.6/site-
packages/django/db/models/sql/query.pyc in get_aggregation(self, using)
371 (alias, self.resolve_aggregate(val, aggregate,
connection=connections[using]))
372 for (alias, aggregate), val
--> 373 in zip(query.aggregate_select.items(), result)
374 ])
375
/home/felipe/.py/2.6/lib/python2.6/site-
packages/django/db/models/sql/query.pyc in resolve_aggregate(self, value,
aggregate, connection)
325 else:
326 # Return value depends on the type of the field being
processed.
--> 327 return self.convert_values(value, aggregate.field,
connection)
328
329 def get_aggregation(self, using):
/home/felipe/.py/2.6/lib/python2.6/site-
packages/django/db/models/sql/query.pyc in convert_values(self, value,
field, connection)
303 it can be overridden by Query classes for specific
backends.
304 """
--> 305 return connection.ops.convert_values(value, field)
306
307 def resolve_aggregate(self, value, aggregate, connection):
/home/felipe/.py/2.6/lib/python2.6/site-
packages/django/db/backends/__init__.pyc in convert_values(self, value,
field)
443 # No field, or the field isn't known to be a decimal or
integer
444 # Default to a float
--> 445 return float(value)
446
447 def check_aggregate_support(self, aggregate_func):
ValueError: invalid literal for float(): c
}}}
and checking queries, I can see that querie are made:
{{{
In [6]: connection.queries
Out[6]:
[{'sql': 'SELECT MAX("webui_link_a"."short_link") AS "short_link__max"
FROM "webui_link_a"',
'time': '0.001'}]
}}}
That's is a small fix, but I think that need to check how act with others
internal types, or default to float only if float(value) don't raise
nothing and just return value if raise.
--
Ticket URL: <http://code.djangoproject.com/ticket/13844#comment:2>
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