Custom HTTP Connector with dynamic data structure

[alelapi]

Hello, I'm implementing a custom HTTP connector that fetches data from an endpoint and returns data with a dynamic structure.
How can I specify the output format?
At the moment I tried to extend the RecordSet and set its properties columnHandles, columnTypes, and byteSource with the new structure and data.
When I run the query, it shows correctly the number of rows processed, but it prints the input table (the one specified in the query) with 0 results.
Is it possible to achieve what I'm trying to do? Do you know what I'm missing?

Example:
SELECT * FROM A WHERE field1 = 'a value'

Should return data with a structure completely different from A fields