presto-main/src/main/java/io/prestosql/sql/gen/JoinCompiler.java/JoinCompiler/CacheKey
class JoinCompiler:        private CacheKey(List<? extends Type> types, List<Integer> outputChannels, List<Integer> joinChannels, Optional<Integer> sortChannel)
        {
            this.types = ImmutableList.copyOf(requireNonNull(types, "types is null"));
            this.outputChannels = ImmutableList.copyOf(requireNonNull(outputChannels, "outputChannels is null"));
            this.joinChannels = ImmutableList.copyOf(requireNonNull(joinChannels, "joinChannels is null"));
            this.sortChannel = requireNonNull(sortChannel, "sortChannel is null");
        }