Conditional execution within a Variable Loop?

I have a pipeline that takes chunks from a database and does some chemical calculations on them.
I have to chunk the data, it is to large to process it in one go, it crashes knime.
For efficiency reasons i prefilter the data, wich leads to empty chunks.

What i would like is to skip the calculation part (wich is taking up quite some processing time even on empty chunks) if the chunk is empty.
But putting an Empty table switch and a Concatenate node in the loop gives the following error:

ERROR     Variable Loop End     Loop End node in inactive branch not allowed.

Is there a way around this ?

Change the concatenate node for the END Case node should help.



Sometimes loop 'oddness' can be resolved by putting the loop into a meta node, or by putting part of the worklow that is inside the loop into a meta node.



Simon: The empty table switch node is not a case node, the end case node does not accept its output.

Sam: I will give that a try, though it is somewhat unsatisfactory that a workflow would work better when you hide the details.