Hello all,

I believe select_related is creating some extraneous joins in situations
where one is joining child models from a base model (model inheritance).

Take the following SQL generated (dpaste here, probably more readable
http://dpaste.com/160677/)

====

SELECT (fields) FROM `base_contact`

LEFT OUTER JOIN `consumer_consumer` ON (`base_contact`.`consumer_id` =
`consumer_consumer`.`id`) # ok

INNER JOIN `agency_program` ON (`base_contact`.`program_id` =
`agency_program`.`id`) # ok

LEFT OUTER JOIN `consumer_contact` ON (`base_contact`.`id` =
`consumer_contact`.`base_id`) # ok

INNER JOIN `base_contact` T5 ON (`consumer_contact`.`base_id` = T5.`id`) # ?!?

# These next two are questionable, since they are joined on a LEFT
OUTER (so they may potentially not be there)

INNER JOIN `consumer_service` ON (`consumer_contact`.`service_id` =
`consumer_service`.`id`)

INNER JOIN `consumer_servicetype` ON (`consumer_service`.`type_id` =
`consumer_servicetype`.`id`)

LEFT OUTER JOIN `IR_contact` ON (`base_contact`.`id` =
`IR_contact`.`base_id`)  # ok

INNER JOIN `base_contact` T9 ON (`IR_contact`.`base_id` = T9.`id`) # ?!?

WHERE `consumer_consumer`.`file` = 06-1757 ORDER BY `base_contact`.`date` DESC

====

There are two joins I simply can't explain (marked "?!?"). Removing them
gives me my expected results. select_related in on case seems to correctly
create a LEFT OUTER, but then follows up by creating an unwanted INNER.

Keep in mind I made a note about the 'questionable' join above, but even
removing that entirely creates the same problem.

I'll be glad to file a ticket, if the issue is something other than my
ignorance.

-Steve

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