First of all, thank you for the fast reply! I'm using NiFi version 1.3.0 and the original column in my table is of type Double. I'm reading out the data by a QueryDatabaseTable processor, afterwards calling a ConvertAvroToJson. To split the array into separete objects I'm using a SplitJson processor. So far, everything seems to be good. Each object looks like this: {"ID":null,"Timestamp":"2017-05-17 17:45:55.0","Name":"asdhybridUL2N","Value":225.0} In order to remove the "ID" attribute (is mostly null and not needed later), adding the "tags" attribute (which shall contain the fix values (a=b, c=d) as shown in the question) and changing "Name" attribute to "metric", I use a mix of UpdateAttribute, AttributesToJson and ReplaceText processors. And that's were the type of the value attribute changes to String. I also saw this JoltTransformJSON processor, but to be honest, I'm not the JSON expert and I didn't understand how to use it in my case.
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