Row count sql fails when in a many-to-many relation, only when it's in a class method

[tominated]

Hey There,

I've got two tables (Posts and Tags), which are related many-to-many (using DMs auto-generated table). Not sure if I need to specify this, but the Tag table only has the name column (no id).

I wanted to make a class method to use in the json output that will return the amount of posts under a tag (so I can output the page count). I put the following method in the Post class:

def self.total_pages
  (self.count / 48).ceil
end

which works when calling Post.total_pages, but not when calling Tag.get('randomtagname'). The following error appears when trying the latter:

DataObjects::SyntaxError: ERROR:  column posts.tag_name does not exist
LINE 1: ...tags" ON "posts"."id" = "post_tags"."post_id" AND "posts"."t...
                                                             ^
 (code: 50360452, sql state: 42703, query: SELECT COUNT(*) FROM "posts" INNER JOIN "post_tags" ON "posts"."id" = "post_tags"."post_id" AND "posts"."tag_name" = 'purplegalaxies' INNER JOIN "tags" ON "post_tags"."tag_name" = "tags"."name" WHERE "post_tags"."tag_name" = 'purplegalaxies', uri: postgres:tom@localhost/hash_tagging?scheme=postgres&user=tom&password=&host=localhost&port=&path=/hash_tagging&query=&fragment=&adapter=postgres)
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-aggregates-1.2.0/lib/dm-aggregates/adapters/dm-do-adapter.rb:20:in `execute_reader'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-aggregates-1.2.0/lib/dm-aggregates/adapters/dm-do-adapter.rb:20:in `block in aggregate'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-do-adapter-1.2.0/lib/dm-do-adapter/adapter.rb:276:in `with_connection'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-aggregates-1.2.0/lib/dm-aggregates/adapters/dm-do-adapter.rb:14:in `aggregate'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-aggregates-1.2.0/lib/dm-aggregates/repository.rb:8:in `aggregate'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-aggregates-1.2.0/lib/dm-aggregates/functions.rb:185:in `aggregate'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-aggregates-1.2.0/lib/dm-aggregates/functions.rb:40:in `count'
  from /Users/tom/Dropbox/Web/blackmilk-repositories/hash-tagging/models.rb:34:in `total_pages'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-core-1.2.0/lib/dm-core/collection.rb:1466:in `block in delegate_to_model'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-core-1.2.0/lib/dm-core/model/scope.rb:53:in `block in with_scope'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-core-1.2.0/lib/dm-core/model/scope.rb:73:in `with_exclusive_scope'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-core-1.2.0/lib/dm-core/model/scope.rb:53:in `with_scope'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-core-1.2.0/lib/dm-core/collection.rb:1465:in `delegate_to_model'
  from /Users/tom/.rbenv/versions/1.9.3-p194/lib/ruby/gems/1.9.1/gems/dm-core-1.2.0/lib/dm-core/collection.rb:1444:in `method_missing'
  from (irb):4
  from /Users/tom/.rbenv/versions/1.9.3-p194/bin/irb:12:in `<main>'

I apologize in advance if this isn't a bug, and it's actually something I've done wrong.

[sheerun]

@tominated Could you post relevant parts of your models + relevant migrations?