def has_run?(filename)
      if @db.schema_schema_evolution_manager_exists?
        query = "select count(*) from %s.%s where filename = '%s'" % [Db.schema_name, @table_name, filename]
        @db.psql_command(query).to_i > 0
      else
        false
      end
    end
def has_run?(filename)
      if @db.schema_schema_evolution_manager_exists?
        query = "select count(*) from %s.%s where filename = '%s'" % [Db.schema_name, @table_name, filename]
        @db.psql_command(query).to_i > 0
      else
        false
      end
    end
True if this script has already been applied to the db. False
 otherwise.