Constant Value Column: Int Variable to Int Column Type causing error


while trying to add an Integer Flow Variable via the Constant Value Column as the same type, I encountered this error:

Invalid settings: Error on creating 'number (integer)' from input string: ''

The Flow Variable clearly is of type int, though.

By switching to string type column however, it works.

I will try to put together an example workflow later.


Hi @mwiegand ,
thank you for your question!
As far as I see you are using old UI of KNIME Analytics Platform, right?
I have looked internally and found the related Jira ticket in our system, describing this issues for version 4._(AP-19105 for internal reference). It seems to me that this issue was addressed in the new version of KNIME Analytics Platform.

I have done the following to test if the problem occurs in KNIME v. 5.1.1:

  1. I have created a fllow variable of a type integer with Variable Creator node:
  2. I have selected it via the flow variable button in the Constant Value Column node:

No problem occurred on my side.
Could you try your WF in the version 5.1.1?

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Hi @mwiegand , as I strongly suspect it is going to take more than this error for you to move to 5.1.1 at this time :wink:

I tried it in 4.7.7, and I guess the following workarounds are an option too

It can be done using two Constant Value Columns…

The first Constant Value column appends the new column of type Integer, using a typed in literal value, e.g. 0

The second Constant Value column then replaces this new Integer column using the value of the variable.

Alternatively of course you could just use String Manipulation and have it use

toInt($${IRandom Values}$$)


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@takbb I working on multiple machines in parallel one of which has 5.1 installed. I just updated to 5.1.1 and created a test workflow which exhibits the same issue. Anyhow, thanks for your suggestion. I think I ended up simply using Rule Engine with TRUE => $VARIABLE$ or something like that.

@darspir I’d personally refrain from calling it old already. It’s the classic interface and is much more mature and stable albeit not as polished. Though, regardless of the UI, the inner workings of Knime respectively the node(s) themself should be identically.

If the UI causes fundamentally different node behavior, I’d be very much concerned as this effectively means there are two applications running in one. In that case, which I mentioned to @DanielBog, splitting classic and modern UI into respective applications should be (just my opinion) absolutely necessary.

Here is the test workflow:


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Hi @mwiegand ,
I have looked into it again and I could reproduce the error, when the append is used instead of replace. This happens because the node itself (internally) does not know whether some values are controlled by a flow variable. Hence, they validate the entry from the main user configuration.

With the modern UI the nodes will still be identical but we will rework the way flow variables (internally) are handled in general and this probably will also account for the issue you have described.
Thank you for your feedback.