The for_save flag wasn't properly propagated when resolving expressions, which
prevented get_db_prep_save() from being called in some cases. This affected
fields like JSONField where None would be saved as JSON null instead of SQL NULL.
Regression in 00c690efbc0b10f67924687f24a7b30397bf47d9.
Thanks to David Sanders and Simon Charette for reviews.
Co-authored-by: Adam Johnson <me@adamj.eu>
The lack of _for_write = True assignment in bulk_update prior to
accessing self.db resulted in the db_for_read database being used to
wrap batched UPDATEs in a transaction.
Also tweaked the batch queryset creation to also ensure they are
executed against the same database as the opened transaction under all
circumstances.
Refs #23646, #33501.
Thanks to Adam Johnson, Carlton Gibson, Mariusz Felisiak, and Raphael
Michel for mentoring this Google Summer of Code 2019 project and
everyone else who helped with the patch.
Special thanks to Mads Jensen, Nick Pope, and Simon Charette for
extensive reviews.
Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
