Hi,
this bothered me for quite a while as, compared to other nodes which show the missing columns highlighted in red, the Column Aggregator node simply losses that information if the columns, went missing:
WARN Column Aggregator 4:1438:0:1458 failed to apply settings: No aggregation method specified. At least one aggregation method is required to perform an aggregation.
Since not even the console log error indicates what has gone missing, there is virtually no way except a very good memory or good enough documentation to reconstruct what has gone missing.
Edit: I partially refine my initial statement as the data gets restored. Another column got included unintentionally which caused the issue. The issue caused here is an incompatibility since the SUM cannot be calculated.
Still, the issue about details going missing prevails which, if fixed, would be a Quality of Live improvement and pays towards “Knime just works” perception.
Bad
Good
Best
Mike