Hi all, I just have to work a with a large panel dataset (left-hand side) to which I would like to join a couple of series from a RHS-dataset. The correct mapping is done via two keys. I did some performance check, and it seems that the current implementation runs the sorting/ mapping for each series joined separately even though a single sorting/ mapping should be sufficient (if I am not wrong). In a first experiment I join all series from the RHS dataset by means of the wildcard operator: <join "@NAME_RHS_DATA" * --ikey=datedim,unitdim> which takes about 5 sec. here. Then I re-run the experiment by successively increasing the number of series to join: <hansl> loop i=1..nelem(RHS_SERIES_NAMES) printf "\nInfo: Start joining %d series.\n", $i flush strings tojoin = RHS_SERIES_NAMES[1:$i] set stopwatch join "@NAME_RHS_DATA" tojoin --ikey=datedim,unitdim printf "\nInfo: Joining took %.2f sec.\n", $stopwatch flush list New = dataset - Base delete New --force endloop </hansl> The output is as follows: <output> Info: Joining all series took 4.91 sec. Info: Start joining 1 series. Info: Joining took 1.91 sec. Info: Start joining 2 series. Info: Joining took 2.88 sec. Info: Start joining 3 series. Info: Joining took 3.88 sec. Info: Start joining 4 series. Info: Joining took 4.84 sec. Script done </output> Do you agree that the sorting or mapping overhead can in principle be reduced when joining multiple series at once? Thanks, Artur