Hi Chris,
Sorry for the unhelpful error message - we’ll have that improved in our next release. In fact in this case it was triggered because you tried to return more than 15Mb of data from a server function. We currently only support payloads up to 4Mb, but we’re working on features to support more.
In the meantime, you should be able to do the data processing you require directly in the function where you call cur.execute. Just don’t return your entire dataset to the client!
Hope that helps. We’ll make sure to keep you updated with new features in this area.