presto-main/src/main/java/io/prestosql/operator/index/PagesIndexBuilderOperator.java/PagesIndexBuilderOperatorFactory/createOperator
class PagesIndexBuilderOperatorFactory:        @Override
        public Operator createOperator(DriverContext driverContext)
        {
            checkState(!closed, "Factory is already closed");

            OperatorContext operatorContext = driverContext.addOperatorContext(operatorId, planNodeId, PagesIndexBuilderOperator.class.getSimpleName());
            return new PagesIndexBuilderOperator(operatorContext, indexSnapshotBuilder);
        }