albertosaurus/pg_comment

module PgComment
  # Extensions to the Rails schema dumper
  module SchemaDumper
    extend ActiveSupport::Concern

    included do
      alias_method_chain :tables, :comments
    end

    # Support for dumping comments
    def tables_with_comments(stream)
      tables_without_comments(stream)
      @connection.tables.sort.each do |table_name|
        dump_comments(table_name, stream)
      end

      unless (index_comments = @connection.index_comments).empty?
        index_comments.each_pair do |index_name, comment|
          stream.puts "  set_index_comment '#{index_name}', '#{format_comment(comment)}'"
        end
      end
    end

    # Dumps the comments on a particular table to the stream.
    def dump_comments(table_name, stream)
      unless (comments = @connection.comments(table_name)).empty?
        comment_statements = comments.map do |row|
          column_name = row[0]
          comment = format_comment(row[1])
          if column_name
            "  set_column_comment '#{table_name}', '#{column_name}', '#{comment}'"
          else
            "  set_table_comment '#{table_name}', '#{comment}'"
          end

        end

        stream.puts comment_statements.join("\n")
        stream.puts
      end
    end
    private :dump_comments

    # Escape out single quotes from comments
    def format_comment(comment)
      comment.gsub(/'/, "\\\\'")
    end
    private :format_comment
  end
end