Sorting on join associations
Reported by David Smalley | September 30th, 2008 @ 12:38 PM
In a project I want to be able to do this....
class Ticket
has n, :ticket_statuses, :order => [:created_at.desc]
has n, :statuses, :through => :ticket_statuses
end
If I call 'ticket.ticket_statuses' I get the following query:
SELECT "ticket_id", "status_id", "created_at" FROM "ticket_statuses" WHERE ("ticket_id" IN ('8D5T-DWUNUG')) ORDER BY "created_at" DESC
But if I call 'ticket.statuses' I get
SELECT "statuses"."id", "statuses"."name", "statuses"."object_class" FROM "statuses" INNER JOIN "ticket_statuses" ON ("statuses"."id" = "ticket_statuses"."status_id") WHERE ("ticket_statuses"."ticket_id" = '8D5T-DWUNUG') GROUP BY "statuses"."id", "statuses"."name", "statuses"."object_class" ORDER BY "statuses"."id"
I then tried to specify the has n, :statuses as:
has n, :statuses, :through => :ticket_statuses, :order => ["ticket_statuses.created_at DESC"] and has n, :statuses, :through => :ticket_statuses, :order => ["ticket_statuses.created_at.desc"]
But both of these fail with
ArgumentError: Unknown property 'ticket_statuses.created_at.desc'
Is it a bug that I cannot apply an order to a join table in this way, or a feature?
Comments and changes to this ticket
-
David Smalley September 30th, 2008 @ 12:39 PM
Formatting seems to be broken, hopefully it still all makes sense.
-
Dan Kubb (dkubb) January 8th, 2009 @ 05:09 AM
- State changed from “new” to “accepted”
- Assigned user changed from “Sam Smoot” to “Dan Kubb (dkubb)”
-
Justin Smestad February 23rd, 2009 @ 04:25 PM
This is still broken on dm-next. I am getting the same error using his script.
/tmp/test-bug > ruby bug.rb [] Included HasAddress into Person [] Included Model into Person [] Included HasEmail into Person [] Included Model into Person [!] Notice how the 'address' property is not present
<PropertySet:{#<Property:Person:type>,#<Property:Person:email>,#<Property:Person:id>}>
-
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Kabari March 8th, 2009 @ 09:37 PM
note This error also happens when adding an attribute to the association ie ":property.not => nil"
-
Dan Kubb (dkubb) June 16th, 2009 @ 03:21 AM
- Milestone set to “0.10.0”
-
Dan Kubb (dkubb) July 23rd, 2009 @ 11:46 AM
- Milestone changed from “0.10.0” to “0.10.1”
-
Dan Kubb (dkubb) October 4th, 2009 @ 09:33 PM
- Milestone changed from “0.10.1” to “0.10.2”
[project:id#20609 not-tagged:"0.10.0" not-tagged:"0.10.1" milestone:id#51895 bulk edit command]
-
Dan Kubb (dkubb) October 6th, 2009 @ 11:41 AM
- Milestone cleared.
- State changed from “accepted” to “suggestion”
- Assigned user cleared.
Currently we do not know if this will be possible outside of RDBMS, so I am marking this as a "suggestion" to revisit later.
With an RDBMS this is trivially simple, you just reference the intermediaries' columns in the ORDER BY, and you get the results back sorted by the intermediary.
With a non-RDBMS, which DataMapper also targets, we don't yet know how m:m relationships will work. It is likely that each intermediary will be fetched, and then joined in-memory with the next relationship in the chain. This will be difficult enough to get right without also throwing intermediary sorting into the mix.
I think this probably will be accepted at some point, it's just that we've got a number of things far more important to resolve first, from self referential m:m, to m:m with non-RDBMS adapters.
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Dan Kubb (dkubb)
Kabari
Piotr Solnica (solnic)
Rick