#4914 ActiveRecord :inverse_of doesn't have any effect - Ruby on Rails

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#4914 open

ActiveRecord :inverse_of doesn't have any effect

Reported by Hongli Lai | June 20th, 2010 @ 06:58 PM | in 3.1

Suppose that a Car has_many Drivers, and that the association methods on both ends have :inverse_of specified. Code here: http://gist.github.com/445969
One would expect that if one references a driver through a car, and then follows the association back to car, no new SQL query would be performed if :inverse_of is set. But a query is performed.

Expected behavior:

car = Car.find(1)
# Car Load (0.3ms)   SELECT * FROM "cars" WHERE ("cars"."id" = 1) 

driver = car.drivers.first
# Driver Load (0.2ms)   SELECT * FROM "drivers" WHERE ("drivers".car_id = 1) LIMIT 1

driver.car
# No SQL query here.

Actual behavior:

car = Car.find(1)
# Car Load (0.3ms)   SELECT * FROM "cars" WHERE ("cars"."id" = 1) 

driver = car.drivers.first
# Driver Load (0.2ms)   SELECT * FROM "drivers" WHERE ("drivers".car_id = 1) LIMIT 1

driver.car
# Car Load (0.2ms)   SELECT * FROM "cars" WHERE ("cars"."id" = 1)

This happens on both Rails 2.3.8 and Rails 3 git master.

Comments and changes to this ticket

Jeremy Kemper June 21st, 2010 @ 01:43 AM
- Milestone set to “2.3.9”
- State changed from “new” to “open”
You flagged this item as spam.
Tor Erik July 2nd, 2010 @ 04:05 PM
- Importance changed from “” to “Low”
Note that it works as expected
```
car.drivers.first
```
is changed to
```
car.drivers.to_a.first
```
You flagged this item as spam.
Tor Erik July 2nd, 2010 @ 04:07 PM
(... it works as expected IF)
Jeremy Kemper August 30th, 2010 @ 02:28 AM
- Milestone changed from “2.3.9” to “2.3.10”
[bulk edit]
Santiago Pastorino February 2nd, 2011 @ 04:49 PM
This issue has been automatically marked as stale because it has not been commented on for at least three months.

The resources of the Rails core team are limited, and so we are asking for your help. If you can still reproduce this error on the 3-0-stable branch or on master, please reply with all of the information you have about it and add "[state:open]" to your comment. This will reopen the ticket for review. Likewise, if you feel that this is a very important feature for Rails to include, please reply with your explanation so we can consider it.

Thank you for all your contributions, and we hope you will understand this step to focus our efforts where they are most helpful.
Santiago Pastorino February 2nd, 2011 @ 04:49 PM
- State changed from “open” to “stale”

holli February 6th, 2011 @ 12:59 AM

State changed from “stale” to “open”

Still open. Noticed it in my code using rails 3.0.3. I did also try it with using the code from above ( http://gist.github.com/445969 ).

Seems like fetching all with .to_a without any other options is the only way to get expected results.

Car.find(1).drivers.first.car
# Car Load (0.2ms)  SELECT "cars".* FROM "cars" WHERE ("cars"."id" = 1) LIMIT 1
# Driver Load (0.2ms)  SELECT "drivers".* FROM "drivers" WHERE ("drivers".car_id = 1) LIMIT 1
# Car Load (0.1ms)  SELECT "cars".* FROM "cars" WHERE ("cars"."id" = 1) LIMIT 1

# This works as excepted, no new query =>
Car.find(1).drivers.to_a.first.car
# Car Load (0.4ms)  SELECT "cars".* FROM "cars" WHERE ("cars"."id" = 1) LIMIT 1
# Driver Load (0.3ms)  SELECT "drivers".* FROM "drivers" WHERE ("drivers".car_id = 1)

Car.find(1).drivers.order('id').to_a.first.car
# Car Load (0.1ms)  SELECT "cars".* FROM "cars" WHERE ("cars"."id" = 1) LIMIT 1
# Driver Load (0.2ms)  SELECT "drivers".* FROM "drivers" WHERE ("drivers".car_id = 1) ORDER BY id
# Car Load (0.2ms)

[state:open]