On Thu, Oct 10, 2013 at 2:55 PM, DJ-Tom <eventel...@gmail.com> wrote:
>
> Thanks, but *how* can I create a hash from a database object in Django - is
> there a generic method to iterate over all (or only specific) fields and get
> a hash value?
>
This is not a full solution, but you can select out extra fields (and
then subsequently filter on them) using the .extra() method on
querysets.
Eg, if you were using mysql and wanted a field that was a hash of pk
(id), first_name and last_name fields, then you could do something
like so:
>>> User.objects.filter(id__lt=10).extra(
... select={'hash': 'MD5(CONCAT(id, first_name,
last_name))'}).values_list('hash')
[('a2147bd4161f55a7ca402d8971b6a45e',),
('663dfc6f51e0ef2c9fa6691527722f20',),
('045dde540781fe013c58c3ebb9383df6',),
('70079b2943da078f437a3678578c78f7',),
('2b997848117758e1844875b1119702bb',),
('2602ecfa423f969614af5b6174c6863e',),
('c9f0f895fb98ab9159f51fd0297e236d',)]
I don't know that this necessarily helps in your aim though. It might
be better to have a custom save method which updates a
"report_fields_modified" timestamp column when fields that affect your
report are modified.
Unfortunately, (IIRC) you cannot easily determine which fields have
been modified without first loading a pristine copy of the object you
are saving from the database, which has obvious performance issues.
Cheers
Tom
--
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 django-users+unsubscr...@googlegroups.com.
To post to this group, send email to django-users@googlegroups.com.
Visit this group at http://groups.google.com/group/django-users.
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-users/CAFHbX1J3ZcNXFGo8y6g9z8z31kpOFfeat0%3DTgOvP51BKUP9C-A%40mail.gmail.com.
For more options, visit https://groups.google.com/groups/opt_out.
