Bug: GroupBy Node Append Elements not working as expected

bug
#1

I have a list column and as aggregation I’m choosing “Append Elements” with “Filter missing collection elements” unchecked.

image

However the generated output list never contains any missing collection elements. Either I don’t understand the option correctly (Filter missing collection elements) or it isn’t working. In fact the option doesn’t have any effect on the output. This applies to KNIME 3.7.2 and KNIME 4 and possibly earlier versions.

See attached workflow for an example.

Append Elements.knwf (8.2 KB)

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#2

The wording should be filter out missing…
If you realy would like to get only thw missing values use the row filter node…

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#3

I want all the collection elements regardless if they are missing or not. See example.

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#4

Hi there,

I have checked it and seems like a bug. Will check it and get back to you.

Tnx for reporting this.

Br,
Ivan

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#5

Hi there,

Just as an alternative approach, I suggest using Ungroup node before the GroupBy node and then use the List method in the GroupBy node. That will solve your issue for now.

:blush:

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#6

Sadly this doesn’t work in my case because I have multiple sub-groups, meaning several columns containing to the same “sub-group” with same amount of elements in the list. One subgroup could have 2 elements and another 10. This leads to additional rows which then when grouping again leads to additional, wrong missing values. So I need to split the table up in these subgroups and then do the ungroup -> group and join again. Safe to say a fix for this issue would help me a lot.

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