I was trying to use the Postrges array_agg() aggregate function against
a column on a related table.
In this case I wanted a list of timestamps from a related table, but I
get an error that the list type is unhashable.
The SQL that SA generates is as expected, and if I replace
func.array_agg with something that
returns a hashable value like func.count() then it works as expected.
Is this a requirement that entities must be hashable? If so can I write
a TypeDecorator that implements __hash__?
My code looks something like this:
qry=session.query(Task, func.array_agg(TaskHistory.updated))
qry=qry.join(Task.History)
qry=qry.filter(Task.priority<5).filter(Task.state!='Approved')
qry=qry.group_by(Task).order_by(Task.asset,Task.name)
results=qry.all()
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/users/dgardner/src/pcs/asset/farm/<ipython console> in <module>()
/usr/lib/pymodules/python2.6/sqlalchemy/orm/query.pyc in all(self)
1265
1266 """
-> 1267 return list(self)
1268
1269 @_generative(_no_clauseelement_condition)
/usr/lib/pymodules/python2.6/sqlalchemy/orm/query.pyc in instances(self,
cursor, _Query__context)
1426
1427 if filter:
-> 1428 rows = filter(rows)
1429
1430 if context.refresh_state and self._only_load_props
and context.refresh_state in context.progress:
/usr/lib/pymodules/python2.6/sqlalchemy/util.pyc in unique_list(seq,
compare_with)
1087 def unique_list(seq, compare_with=set):
1088 seen = compare_with()
-> 1089 return [x for x in seq if x not in seen and not seen.add(x)]
1090
1091 class UniqueAppender(object):
TypeError: unhashable type: 'list'
--
David Gardner
Pipeline Tools Programmer
Jim Henson Creature Shop
dgard...@creatureshop.com
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