id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
30319	model.save() surprising behavior with update_fields specified and auto_now field in model	sebhaase	nobody	"In section ""Specifying which fields to save"" ([https://docs.djangoproject.com/en/dev/ref/models/instances/#specifying-which-fields-to-save]) it reads that `update_fields` can be specified mostly for performance benefits...

However, I found that regarding a field with `auto_now=True` there is a different outcome.
IOW, specifying `update_fields` can be used to keep the old date in respective  ""auto_now=True""-field UNLESS that field is also explicitly given un `update_fields`

This should be more prominently stated in the documentation.

In addition I also noticed that - using deserialization - `object.save()` gives unexpected different results for auto_now field: 
 - if the object-pk already exists , the field is saved as given 
 - but if it does not exist, the given value is ignored, and the current time is used instead 
... very strange if you ask me...

refs: 
[https://stackoverflow.com/questions/17474057/enforce-auto-now-when-using-saveupdate-fields]
[https://groups.google.com/d/msg/django-users/sqMrUlZP2-8/FczIEwwMBAAJ]
"	Uncategorized	closed	Database layer (models, ORM)	2.1	Normal	wontfix		seb.haase+django@…	Unreviewed	0	0	0	0	0	0