Question about Column appender

Hi all!
New there on the forum. It’s a pleasure to be part of the community!
Just a quick question about how the Column appender node works.
As far as i understanded the inputs of a knime node are read only. If so, does that mean that when i append a column to a table that table gets reconstructed from 0 to build the output with the column appended?
I’m just trying to understand that to optimize my workflow as much as possible. I recursively add one column at a time after checking a variable. That is representing a bottleneck for me so understanding exactly how the column appender behaves could help me trying to find a better implementation of my workflow.

Thanks in advance!!

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hi frog,

welcome to the community. as far as i understood, table appender just add the rows of one table to another on. for this both tables needs to be sorted in the same way to get the values in the right place.

alternativ you could use joiner node.


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Hi @frog,
In the case of the Column Appender the table is really created from scratch (code is here). But I think this is not the case for every node. Imagine a node that simply appends another column, without caring for RowIDs. This node could simply create an augmented table by referring to the original, still unchanged, table when accessing columns present there and referring to the new column when that one is accessed. It does not violate the immutability of the first table but still saves a lot of memory. However, if this is done that way depends on the implementation of the node and as soon as the table is serialized to disk the reference to the old table has to be resolved and the whole table has to be written.
Kind regards

Edit: “implementation of the node”, not “implementation of the table”


Thank you very much for the reply @AlexanderFillbrunn . Super clear!



Hi there @frog,

regarding optimizing your workflow. You can always share you workflow (or part that needs optimization) here and will get ideas/suggestions/modified workflow :wink:



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