Nicely formatted version:
http://stackoverflow.com/questions/24930155/strange-error-after-sqlalchemy-update-list-object-has-no-attribute-all-colu
After updating to the most recent SQLAlchemy one of my slightly more
complex query started to fail with an error inside SQLalchemy.
Here's a simplified version of my query:
subquery = (select(['latitude'])
.select_from(func.unnest(func.array_agg(Room.latitude))
.alias('latitude')).limit(1).as_scalar())
Room.query.with_entities(Room.building,
subquery).group_by(Room.building).all()
When executing it I get an error deep inside SQLAlchemy:
File ".../sqlalchemy/sql/selectable.py", line 429, in columns
self._populate_column_collection()
File ".../sqlalchemy/sql/selectable.py", line 992, in
_populate_column_collection
for col in self.element.columns._all_columns:
AttributeError: 'list' object has no attribute '_all_columns'
Inspecting it in a debugger shows me this:
>>> self.element
<sqlalchemy.sql.functions.Function at 0x7f72d4fcae50; unnest>
>>> str(self.element)
'unnest(array_agg(rooms.id))'
>>> self.element.columns
[<sqlalchemy.sql.functions.Function at 0x7f72d4fcae50; unnest>]
The problem started with SQLAlchemy 0.9.4; in 0.9.3 everything worked fine.
When running it in SQLAlchemy 0.9.3 the following query is executed (as
expected):
SELECT rooms.building AS rooms_building,
(SELECT latitude
FROM unnest(array_agg(rooms.latitude)) AS latitude
LIMIT 1) AS anon_1
FROM rooms
GROUP BY rooms.building
Am I doing something wrong here or is it a bug in SQLAlchemy?
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