Redmine

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