Group Loop Start node autocasts Path columns

when solving the Just KNIME It! challenge #2 I discovered something I’d describe as bug:
Using as few nodes as possible, I relied upon the filename as grouping column for the Group Loop Start. To skip any type conversions, it was already a Path column. However, the Group Loop Start changed the type of the corresponding Flow Variable to type String. There’s one Flow Variable for each grouping column, and a group identifier variable. I’m talking about the former.

This also happens with other data types:

  • Long gets cast to double
  • bools gets cast to int

I checked the Table Row to Variable (Loop Start), it does none of these conversions. Date&Time columns are changed to string in all 3 nodes, so that’s consistent.
Is there a reason for this behaviour or is it actually a bug? :slight_smile:

JKI_002.knwf (250.9 KB)