cleanup migration to go with 70c18ac

does the work that group_category_data_migration pre-70c18ac missed,
no-op if group_category_data_migration post-70c18ac was run

Change-Id: I39cc35cf385857f11cdcbdab3c462dbff9c4ce12
Reviewed-on: https://gerrit.instructure.com/6235
Tested-by: Hudson <hudson@instructure.com>
Reviewed-by: Brian Palmer <brianp@instructure.com>

db/migrate/20111017124400_group_categories_cleanup_migration.rb

@@ -0,0 +1,43 @@
+# an older version of 20111007115901_group_categories_data_migration.rb was
+# broken and did not update assignments correctly. the current version is
+# fixed, but if you ran the broken one, this will clean it up. if you ran the
+# fixed one, this migration is a no-op.
+class GroupCategoriesCleanupMigration < ActiveRecord::Migration
+  def self.uncached_group_category_id_for(context, name)
+    if !context.is_a?(Account) && name == "Student Groups"
+      GroupCategory.student_organized_for(context).id
+    elsif name == "Imported Groups"
+      GroupCategory.imported_for(context).id
+    else
+      context.group_categories.find_or_create_by_name(name).id
+    end
+  end
+
+  def self.group_category_id_for(record)
+    context = record.context
+    name = record.group_category_name
+    @cache ||= {}
+    @cache[context] ||= {}
+    @cache[context][name] ||= uncached_group_category_id_for(context, name)
+  end
+
+  def self.update_records_for_record(record)
+    return unless record.context.present? and record.group_category_name.present?
+    category_column = (record.class == Group ? 'category' : 'group_category')
+    records = record.class.scoped(:conditions => ["context_id=? AND context_type=? AND #{category_column}=? AND group_category_id IS NULL",
+      record.context_id,
+      record.context_type,
+      record.group_category_name])
+    records.update_all({:group_category_id => group_category_id_for(record)})
+  end
+
+  def self.up
+    Assignment.find(:all, :select => "DISTINCT context_id, context_type, group_category",
+      :conditions => ['context_id IS NOT NULL AND group_category IS NOT NULL AND group_category_id IS NULL']).each do |record|
+      update_records_for_record(record)
+    end
+  end
+
+  def self.down
+  end
+end