Skip transaction creation for single statement operations
|Reported by:||Anssi Kääriäinen||Owned by:||nobody|
|Component:||Database layer (models, ORM)||Version:||1.5|
|Has patch:||no||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
There are a couple of cases where Django will execute just a single data modifying statement for the operation done. Examples include single table .save(), .delete() that doesn't cascade, bulk_create() and .update(). Atomicity of single statements guarantees that these operations work without creating / releasing transaction. This could increase performance of these statements when used in autocommit mode.
The save() method should be easy to handle - it is easy to check if the table has parents or not. Bulk create is also somewhat easy, although there are cases where multiple queries need to be executed. Model deletion might be hard to handle, signals are sent inside the same transaction and it isn't that far fetched to think that signal handler will do additional data modifications (log changes for example).
It might be there are more operations that could benefit from this - get_or_create() and update_or_create() for example.
I got the idea while inspecting if cache db backend could use ORM directly. Currently the db backend doesn't wrap all data modifications in atomic blocks, but if using ORM directly that would happen and this could lead to performance problems in the backend.