presto-main/src/main/java/io/prestosql/operator/MultiChannelGroupByHash.java/MultiChannelGroupByHash/hashPosition
class MultiChannelGroupByHash:    private long hashPosition(long sliceAddress)
    {
        int sliceIndex = decodeSliceIndex(sliceAddress);
        int position = decodePosition(sliceAddress);
        if (precomputedHashChannel.isPresent()) {
            return getRawHash(sliceIndex, position);
        }
        return hashStrategy.hashPosition(sliceIndex, position);
    }