File Download Widget

Hi All,

I am connecting my impala database , performing some operations and then writing to a csv in my local system. To allow multiple users to download the final file in their local systems i included a file download Widget , connected it to CSV writer and then turned it into a component.
However, on the web portal this is the error i am coming across. Can someone explain with an example what am i doing wrong in this and the logic behind it?

*** WARNING Impala Connector 235:1: The input data type mapping configuration is not valid.**
*** WARNING Component Input 235:18:0:18: Component does not have input data, execute upstream nodes first**
*** WORKFLOW ERROR: Further workflow execution is not possible. Please check the workflow.**

Hi @r_jain

Explaining with an example what you are doing wrong without providing any details on what you current have is a bit tricky :wink:

The log gives you an indication that your impala query is not fully compatible and as such the downstream nodes did not get fed with data. This is very likely to be reason the File Download Widget does not have anything to work with subsequently.

Have a look on the KNIME Hub, there is a large variety of example workflows that utilizes the File Download Widget.

If this isn’t sufficient, I’m sure there are people here to help but that would go best with some more specific input from your side.

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Hi,

I am doing the exact same thing and not sure what’s the issue with Impala. Do the database also need to reside under a component or its not required?

The error doesn’t come up when i run locally. Only on the server.

@ArjenEX So i have an update on this. The issue is with the data type mapping for some field.
Earlier i was doing a select * from table which has 110 columns, but to test the feature i restricted to just 4 columns and it worked.
The question now is which are the columns that are causing the issue and how do i identify those, so i can add them up to the mapping configuration?

Thanks.
R

What I would do in that case is get the table properties and see if there is any obscure data type which is likely to be not recognized by KNIME.

I have not used Impala before but it appears that the DESCRIBE query should get you this information.

https://impala.apache.org/docs/build/html/topics/impala_describe.html

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