Records created through a call to .save() don't share their _ids
When creating a bunch of records through calling save()
each records is set in its own small browse list.
This can have a performance impact if later the code loops over the list of records and make some database access on it.
The proposed patch will share the same list for each records that would have been in its own browse list (this is to prevent the case where the developer has explicitly used the _ids
kwargs when creating the records).