--(Unsigned mail from my phone) -------- Original message --------From: Ryan Nowakowski <[email protected]> Date: 13/6/22 07:09 (GMT+10:00) To: [email protected] Subject: Re: How to hash fields and detect changes in a record On Sat, Jun 11, 2022 at 12:13:16AM +1000, Mike Dewhirst wrote:> On 10/06/2022 11:24 pm, Ryan Nowakowski wrote:> > On Fri, Jun 10, 2022 at 05:52:48PM +1000, Mike Dewhirst wrote:> > > I think the solution might be to hash note.title and note.note into a new> > > field note.hash on being auto-created. On subsequent saves, compare the> > > latest hash with note.hash to decide whether to delete auto-inserted notes> > > prior to generating the next set. Those subsequent saves could be months or> > > years later.> > Hashing is useful if you want to check that something has been> > unexpectedly changed. I assume the note can only be changed through> > your web app so you know when a user is changing a note.> > These are automatically generated notes which taken together constitute> advice on how to deal with the analysis. Users can edit them. For example,> someone might record some action taken regarding the advice. I don't want to> delete that. If nothing has been edited, it is safe to delete.> > So how do I know it is the same as when originally generated - and safe to> delete - except by storing a hash of the interesting fields.Because when the user edits a note, during the form.save()(assumingyou're using Django forms), you'll set `altered_by_user` to True.Notes can also be altered in the Admin> And if that is the best approach, what sort of hashing will survive Python> upgrades etc?Pick a hash algorithm[1](ex: sha256). The output will remain the sameeven with Python upgrades.So the mechanism doesn't need to be a hash - as you said. I now just sum ord(char) for the title and the note and keep that in a flag field.Only the auto-notes get a flag because they are the only ones I would consider deleting. [1] https://docs.python.org/3/library/hashlib.html> > Since you're> > expecting users to change some of the notes and you know when they do,> > hashing might be overkill. Instead, add a boolean `altered_by_user`> > field to the note model. Initially when you automatically create the> > note altered_by_user would be set to False. If a user changes the note,> > set altered_by_user to True.>> Not sure this would work. Note creation and eventually automatic deletion is> all driven from model methods executed on saving.Why wouldn't this work? During note creation, altered_by_user would beset to False automatically because that's the default. Whenautomatically deleting, do: Note.objects.filter(altered_by_user=False).delete()-- You received this message because you are subscribed to the Google Groups "Django users" group.To unsubscribe from this group and stop receiving emails from it, send an email to [email protected] view this discussion on the web visit https://groups.google.com/d/msgid/django-users/20220612210931.GA32625%40fattuba.com.
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