[Sqlalchemy-tickets] [sqlalchemy] #1688: Query.one() fails to raise MultipleResultsFound

[sqlalchemy <mi...@zz...>]

#1688: Query.one() fails to raise MultipleResultsFound
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 Reporter:  guest   |          Owner:  zzzeek                
     Type:  defect  |         Status:  new                   
 Priority:  medium  |      Milestone:                        
Component:  orm     |       Severity:  no triage selected yet
 Keywords:          |   Status_field:  awaiting triage       
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 G'day,

 I've got a situation where a query results in multiple rows, but calling
 one() does not result in a MultipleResultsFound exception being raised.

 I am using polymorphic mapping and then joining the 'base' table with one
 of the 'identity' tables. (Please see the attached unit test which I
 believe illustrates the problem clearly).

 I can confirm that two rows are returned by the database, but these rows
 are put into an IdentitySet and happen to be equal due to the query only
 selecting columns from the base class (this is why the problem only
 manifests when using polymorphic mapping). This causes the call
 to one() to return a single row '''even though each row results in a
 different object once mapped polymorphically'''. I am aware that the query
 is not well constrained (it should explicitly join on the two tables where
 Node.node_id==BranchOffice.node_id) but I guess that the assertion aspect
 of using one() should catch the problem in my query.

 I've also attached a patch containing the fix that I have deployed here,
 but I am by no means certain that it is the best solution.

 Please let me know if I can provide any extra information, try another
 solution or whatever.

 Regards,
 David Jagoe

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Ticket URL: <http://www.sqlalchemy.org/trac/ticket/1688>
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