presto-main/src/main/java/io/prestosql/operator/MultiChannelGroupByHash.java/MultiChannelGroupByHash/appendValuesTo
class MultiChannelGroupByHash:    @Override
    public void appendValuesTo(int groupId, PageBuilder pageBuilder, int outputChannelOffset)
    {
        long address = groupAddressByGroupId.get(groupId);
        int blockIndex = decodeSliceIndex(address);
        int position = decodePosition(address);
        hashStrategy.appendTo(blockIndex, position, pageBuilder, outputChannelOffset);
    }