Loop End - Queued Issue

Hi there

I am currently facing an issue with the Loop End node not progressing past the “queued” status.

I have created a relatively simple loop that starts by using the “List Files/Folders” and then connects to a “table row to variable loop start”. This just reads a list of files in a folder and uses the path as the flow variable to loop in my excel reader. I then end this with the Loop End node.

The loop appears to work fine when I read two (2) files, however when I add a third (3rd) file the Loop End appears to just hang at the queued stage and nothing happens. I’ve tried various files and combination and each time it appears to get stuck on the third iteration.

I am using KNIME v4.7.1.

Just not sure if this is a bug or something in my configurations, but trying various configuration settings on the Loop End doesn’t appear to resolve the issue.

Any help would be greatly appreciated.

Hello @Gav and welcome to the KNIME Community

The Loop End node works aggregating data frames that are compatible in columns and format type.

It does happen that leaving the reader as its own, if your data is not clean enough (column names, some text in a column of numbers, undefined format (?) because empty column in one of the files…) creates a row bind conflict in Loop End node.

You can inspect the first run of your Excel Reader node and compare with the reading when the error shows up.

It’s hard to guess without some more information, but some actions to normalize the data inside the loop must be taken.

A good test and maybe a solution, is forcing the Excel Reader to import all the columns as string (system regional decimal format recommended to be in English for numbers); you can set it in the Transformation tab inside the Excel Reader.

Before the Loop End, you can use a String to Number node. Selecting the columns to be imported as numeric. Doing in this way you will get an uniform feed for the Loop End function.

I hope this can help

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If you upload your flow (no sensitive data rather dummy if nessecary ) then you get a helpful response probably sooner.

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