Looping of File Reader is slow


I used a List Files node and then loop over few thousand .csv files (small file sizes). Looping is very slow (~1 per sek), if the Loop End node is connected to the rest of the workflow. If I delete the connection between Loop End and the following node, it immediately goes 20-30-times faster. It seems that KNIME checks the configuration state of the downstream nodes each iteration. I noticed that especially String Manipulator nodes behind Loop End slows down looping. 

I am running KNIME on a MAC and sometimes notice bad performace, which I suppose is due to the OS. However, this issue looks like a KNIME (String Manipulator) thing...



Hello Martin,

interesting... - but we have trouble reproducing this effect. It could be related to the type of loop nodes that you are using, could you post/send the workflow or at least an image of the relevant parts?

Thanks! Michael

Hello Michael,

I could reproduce this effect on another MAC, on Windows and also loafin files from local HHD instead of from server. Here is the workflow and 100 .txt files in a folder, zipped. I hope this helps to trouble shoot this...





Hi Martin, 

Thanks for the repot, we've ientified and fixed the bug.  The fix will be available in KNIME 2.8 which is due out very soon.




Aaron Hart

Hello Martin,

in the meantime you can also avoid this problem by adding a "Domain Calculator" node to your workflow, right behind the LoopEnd node.

Cheers, Michael