Support RETURNING for SQLite

[bouk]

@billy1624 I'm not sure what the original problem was, but could RETURNING be supported for SQLite now?

Motivation

I have a query that has an ON CONFLICT and I want to use exec_with_returning, however last_insert_rowid is not set for SQLite when there's a conflict, so there's no way to figure out which row was updated. My query looks like:

Model::insert().on_conflict(...).exec_with_returning(db)

This works fine on Postgres but not SQLite

Proposed Solutions

Get RETURNING working for SQLite

Current Workarounds

You can do an extra SELECT query instead of using ON CONFLICT

[tyt2y3]

I think the blocker is we needed a way to tell if the linked SQLite version supports RETURNING and adjust the logic accordingly on compile time.

A less ideal solution would be to detect that on runtime, and adjust the logic accordingly. This would actually be a bigger change.