upsert directly calls create if id column is not specified

There's cases where I would want to use upsert without the id column being specified. An example of this is having an auto_increment SQL column that has other unique indexes that are not id.

Look at the upsert implementation in the ORM's codebase, likely in a database adapter like mysql or postgres. Identify where the id column check occurs and how it falls back to create. Review the schema handling for auto_increment and unique indexes. Test with a model that has a non-id unique index to see the current behavior.

Scritto dal modello di indicizzazione a partire dal testo della issue.