Diesel is nowhere near being able to fully map SQL to rust. It's ok for relatively simple queries that are typical for OLTP applications. Anything beyond that and you're going to run into trouble.

If you want to do something more OLAP-ish or insert data in bulk, you have a huge problem. SQLAlchemy is far better, even though SQLAlchemy also has its own share of limitations (dealing with jsonb_to_recordset and functions like it for example).