presto-main/src/main/java/io/prestosql/operator/SetBuilderOperator.java/SetBuilderOperator/SetBuilderOperator
class SetBuilderOperator:    public SetBuilderOperator(
            OperatorContext operatorContext,
            SetSupplier setSupplier,
            int setChannel,
            Optional<Integer> hashChannel,
            int expectedPositions,
            JoinCompiler joinCompiler)
    {
        this.operatorContext = requireNonNull(operatorContext, "operatorContext is null");
        this.setSupplier = requireNonNull(setSupplier, "setProvider is null");
        this.setChannel = setChannel;

        this.hashChannel = requireNonNull(hashChannel, "hashChannel is null");
        // Set builder is has a single channel which goes in channel 0, if hash is present, add a hachBlock to channel 1
        Optional<Integer> channelSetHashChannel = hashChannel.isPresent() ? Optional.of(1) : Optional.empty();
        this.channelSetBuilder = new ChannelSetBuilder(
                setSupplier.getType(),
                channelSetHashChannel,
                expectedPositions,
                requireNonNull(operatorContext, "operatorContext is null"),
                requireNonNull(joinCompiler, "joinCompiler is null"));
    }