Rule engine: column name from flow variable

Hi everybody,

Using the rule-based row filter, is it possible to check for a missing value in a column for which I get the name from a flow variable?

Usually, the syntax to check for missing values in column "col" would be:


The syntax to use a String flow variable "var" in the rule engine is


Therefore, if "var" contains the name of the column I want to check, I would do something like

MISSING $${Svar}$$ => TRUE

However, this gives the error message: "MISSING operator requires a column".

Thanks for any advice, Andreas

No, you have to create the rule as a flow variable (for example with the Java Snippet Variable, like return "MISSING $" + columnName + "$ => TRUE";) and replace the rule in the Rule-based Row Filter using that string. This is a bit error-prone to do (especially the flow variable creation and selecting the proper element in the array), but I have no better option, as the node do not allow embedded evaluation, which would be something like $$${Svar}$$$ to select a column. I guess this would be possible to implement, but wold be really hard to understand.

Thank you, I managed to get it done this way!

Hi, I agree with choc.2000 that it would be very useful if the Rule-based Row Filter node would support direct use of flow variables. I would like to use this within a Column List loop to filter out all rows with missing values, column by column.


Hi there @evert.homan,

agree with you but seems to me you can also use Row Filter for your use case.


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Row Filter (Labs) can maybe do it. The regular Row Filter can only filter based on one column at a time as far as I know.


Hi @evert.homan,

but my impression was you are running a column list loop and filtering missing values. That is way I suggested Row Filter where you can control column name with current column name flow variable.


You are very right of course. Still, use of flow variable directly in the Rule-based Row Filter node would be very useful.


Hi @evert.homan,

agree :slight_smile:


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