Warnings on Variables in a Loop

Hi all,

I’ve created a simple loop to import several CSV files and also capture the file name of each file to identify the record data origin.

The loop seems to be working fine but I am getting warnings. I want to check whether these are an issue, or whether there is a better approach.

My current approach:

  1. Feed a list of files into a chunk loop (these automatically seem to convert to Path type)
  2. Convert path into variable using Table Row to Variable
  3. The path is fed to the CSV Reader to select the file for import
  4. I use Path to String (Variable) to capture the file path as a string and use this in the Constant Value Column.

I am getting the following warnings:

  1. WARN Path to String (Variable) - No path variables selected.
  2. WARN CSV Reader - The stored spec has not been created with the given file/path.
  3. WARN CSV Reader - Errors overwriting node settings with flow variables: Unknown variable “Path”

Thanks for your guidance!

Hi @sjmartin

Are you getting the expected outcome of the loop? KNIME in general really likes to let the user know anything that might be happening out of expected, even if this does not affect the result. It is, in the end, good as you will always be warned and always be aware if there is something that could potentially be a problem.

I think your approach seems to be a solid approach for me. That said, some of your warnings seem to be related with the variable Path not existing. Can you share a minimal reproducible example of your workflow?

I experienced the similar problem.

In fact, the CSV reader node does not function properly. The CSV reader node somehow remembers the spec/structure of the CSV file it previously read-in and affect the CSV file imported in the current iteration.

Is there anyway to get this resolved?

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Hello @christine_ywl

with the List Files/Folders Node and after that the Table Row To Variable Loop Start.


In the CSV Reader activate the variable setting. Here you can choose the Path variable.

Greetings, Brotfahrer

Hello christine_ywl,
just enable the Support changing file schemas option on the Advanced tab of the reader in which case the node does not output a table specification during configure but can handle changing file structres. For more details see the File Handling documentation.


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