Problem with Rule Engine in Loop

I’m trying to use the Rule Engine node inside a Column List Loop. The Rule Engine works fine without a loop, but doesn’t calculate correctly inside a loop. Here are screenshots. I’d really appreciate some help.

No loop rule.

No loop results

Loop rule.

Loop Results.

Hi @rfeigel

I assume that you want to do the same transformation on every column within a Column List Loop. To get it working you need to rename the current column name (=flow variable) to some generic name. Your operation is always (every column) on the column with the generic name. At the end you have to revert this name to the “current column name”.
column_list_loop.knwf (26.4 KB)

gr. Hans


Hello @rfeigel,

Flow variable holding column name doesn’t reference column values in Rule Engine node.

For possible approach avoiding loop in these cases see here:



Just to add to the solutions here and share my thoughts (in case anyone is interested :wink: )
If your condition is simple I would go with Math Formula multi column and a simple if statement


Then we avoid any computational expensive operation


@HansS @ipazin @Daniel_Weikert
Thanks to you all for the ideas. I’m pondering how to proceed. Each column has a lot of downstream processing after this initial flag is set which makes me lean towards a loop. I’ll post my final approach.


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