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