presto-main/src/main/java/io/prestosql/operator/InterpretedHashGenerator.java/InterpretedHashGenerator/hashPosition
class InterpretedHashGenerator:    public long hashPosition(int position, IntFunction<Block> blockProvider)
    {
        long result = HashGenerationOptimizer.INITIAL_HASH_VALUE;
        for (int i = 0; i < hashChannels.length; i++) {
            Type type = hashChannelTypes.get(i);
            result = CombineHashFunction.getHash(result, TypeUtils.hashPosition(type, blockProvider.apply(hashChannels[i]), position));
        }
        return result;
    }