Chris@1115: class AddUniqueIndexToIssueRelations < ActiveRecord::Migration
Chris@1115:   def self.up
Chris@1115: 
Chris@1115:     # Remove duplicates
Chris@1115:     IssueRelation.connection.select_values("SELECT r.id FROM #{IssueRelation.table_name} r" +
Chris@1115:       " WHERE r.id > (SELECT min(r1.id) FROM #{IssueRelation.table_name} r1 WHERE r1.issue_from_id = r.issue_from_id AND r1.issue_to_id = r.issue_to_id)").each do |i|
Chris@1115:         IssueRelation.delete_all(["id = ?", i])
Chris@1115:     end
Chris@1115: 
Chris@1115:     add_index :issue_relations, [:issue_from_id, :issue_to_id], :unique => true
Chris@1115:   end
Chris@1115: 
Chris@1115:   def self.down
Chris@1115:     remove_index :issue_relations, :column => [:issue_from_id, :issue_to_id]
Chris@1115:   end
Chris@1115: end