#2960 uniq bug on array of ActiveRecord Objects - Ruby on Rails

Type	To find
responsible:me	tickets assigned to you
tagged:"@high"	tickets tagged @high
milestone:next	tickets in the upcoming milestone
state:invalid	tickets with the state invalid
created:"last week"	tickets created last week
sort:number, importance, updated	tickets sorted by #, importance or updated
Combine keywords for powerful searching.
Use advanced searching »

This project is archived and is in readonly mode.

#2960 ✓wontfix

uniq bug on array of ActiveRecord Objects

Reported by Peter Leonhardt | July 27th, 2009 @ 09:41 PM

The uniq method on collections of ActiveRecord Objects relies on the primary_key of the model to determine if two objects are the same.

This can lead to problems if the table does not have an 'id' column, and set_primary_key is not defined, or if the table uses a composite key.

This really boils down to a problem with ==, but manifests in [].uniq

For example,
If you have a table "items" without a column 'id'

  Item.create(:some_id => 1, :name => "Item 1")
  Item.create(:some_id => 2, :name => "Item 2")

  a = Item.find_by_some_id(1)
  b = Item.find_by_some_id(2)
  a == b #=> true, expected FALSE

In most cases, it is a simple case of utilizing 'set_primary_key', however, when one is interfacing with legacy databases with composite keys? It is also unexpected behavior. There is nothing similar between the two objects besides that they are the same class.

I'm not sure what the proper solution would be. If the primary_key doesn't match any columns, compare values of the attributes? I'll leave that up to debate.

Demo Attached, just rake db:migrate

uniq_demo.zip 93 KB

Comments and changes to this ticket

Michael Koziarski August 3rd, 2009 @ 06:02 AM
- Tag changed from “active_record, array” to “active_record, array, bugmash”
You flagged this item as spam.
Cristi Balan August 8th, 2009 @ 12:08 PM
-1

Since composite keys are not part of AR core, but added through plugins, I think the equality of records should be handled in the same plugin as well by overriding ==.
You flagged this item as spam.
John Pignata August 9th, 2009 @ 05:58 AM
-1

Where composite keys or Rails-known primary keys aren't used, == should be overriden.
You flagged this item as spam.
Kieran P August 9th, 2009 @ 06:22 AM
-1 In agreement with Cristi and Johns comments. If you're needing this, overwrite the functionality in your own code since its a limited case.
Rizwan Reza August 9th, 2009 @ 11:24 PM
not reproducible

-1 Agreed with Cristi... it's a job of a plugin.
Jeremy Kemper August 9th, 2009 @ 11:26 PM
- State changed from “new” to “wontfix”
- Tag changed from “active_record, array, bugmash” to “active_record, array”
- Milestone cleared.