presto-main/src/main/java/io/prestosql/operator/JoinOperatorFactory.java/OuterOperatorFactoryResult/OuterOperatorFactoryResult
class OuterOperatorFactoryResult:        public OuterOperatorFactoryResult(OperatorFactory outerOperatorFactory, PipelineExecutionStrategy buildExecutionStrategy)
        {
            this.outerOperatorFactory = requireNonNull(outerOperatorFactory, "outerOperatorFactory is null");
            this.buildExecutionStrategy = requireNonNull(buildExecutionStrategy, "buildExecutionStrategy is null");
        }