piece
The join: for each source key, merge the HyperLogLog sketches via element-wise max (HyperLogLog.piece). Keys present in only one side are taken as-is (the other side's implicit empty sketch contributes nothing).
The join: for each source key, merge the HyperLogLog sketches via element-wise max (HyperLogLog.piece). Keys present in only one side are taken as-is (the other side's implicit empty sketch contributes nothing).