presto-main/src/main/java/io/prestosql/operator/MultiChannelGroupByHash.java/MultiChannelGroupByHash/getRawHash
class MultiChannelGroupByHash:    private long getRawHash(int sliceIndex, int position)
    {
        return channelBuilders.get(precomputedHashChannel.getAsInt()).get(sliceIndex).getLong(position, 0);
    }