You can override the save method or simply use Django signals <https://docs.djangoproject.com/en/2.1/topics/signals/> to modify fields of Model automatically.
On Thu, Mar 21, 2019 at 8:21 PM Derek <[email protected]> wrote: > Your use case is not very clear. > > If you are simply "running a few trivial calculations and storing the > info" then you could use a function in the database to do this for you - > pulling data directly from Table A and storing the result in Table B. Data > in Table B could then be later edited using the usual Django functionality. > > As a side note: a trip to the database to get data is not "useless" if > you need that data for some reason and it is not already present in your > app. > > On Thu, 21 Mar 2019 at 19:06, Dylan Young <[email protected]> > wrote: > >> For example using made-up syntax: >> >> Entry.objects.create(start=F(Recurrence.objects.filter(pk=r_id), >> 'start_time')) >> >> Note that we can't use `get` since the whole point is to avoid all the >> useless round-trips to the DB. >> >> Best, >> >> Casey >> >> On Thu, 21 Mar 2019 at 13:18, Dylan Young <[email protected]> >> wrote: >> >>> It's not a recalculation. It's instantiation. >>> >>> Instance data diverges from the factory data and needs to be >>> independently editable. >>> >>> Best, >>> >>> Casey >>> >>> Le jeu. 21 mars 2019 2:52 a.m., Derek <[email protected]> a écrit : >>> >>>> Permanently storing data that can be recalculated from existing data is >>>> a practice specific to the needs of particular applications. >>>> >>>> Have you perhaps considered making use of the "view" table >>>> functionality available in most databases? >>>> >>>> For example, in PostgreSQL you can create a materialized view which >>>> "caches the result of a complex expensive query and then allow you to >>>> refresh this result periodically." - see >>>> http://www.postgresqltutorial.com/postgresql-materialized-views/ >>>> >>>> >>>> On Tuesday, 19 March 2019 17:34:11 UTC+2, Dylan Young wrote: >>>>> >>>>> Hey all: >>>>> >>>>> I often find myself fetching data from models in the database only to >>>>> run a few trivial calculations and store the info in a different model. >>>>> >>>>> Is there an established ORM pattern for directly creating objects in >>>>> the DB based on the fields of other models? >>>>> >>>>> Sorry if this is obvious, but I couldn't find much on this in my web >>>>> searching. >>>>> >>>>> >>>>> Best, >>>>> >>>>> Casey >>>>> >>>> -- >>>> 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]. >>>> To post to this group, send email to [email protected]. >>>> Visit this group at https://groups.google.com/group/django-users. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/django-users/a1c55adc-c5fa-465c-8740-3a741bc22686%40googlegroups.com >>>> <https://groups.google.com/d/msgid/django-users/a1c55adc-c5fa-465c-8740-3a741bc22686%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> For more options, visit https://groups.google.com/d/optout. >>>> >>> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "Django users" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/django-users/RDU_KsRqd90/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at https://groups.google.com/group/django-users. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/django-users/CAPGJNu40H%3Du5bLLUYYosHpKNDsH7xMFPg-7GU%2B_fHCV59SknyA%40mail.gmail.com >> <https://groups.google.com/d/msgid/django-users/CAPGJNu40H%3Du5bLLUYYosHpKNDsH7xMFPg-7GU%2B_fHCV59SknyA%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> For more options, visit https://groups.google.com/d/optout. >> > -- > 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]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/django-users. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-users/CAF1Wu3NkZCsU8oxLnuGPBtkWpPnq_L_H-o2dVb1rMUjm0pdW3A%40mail.gmail.com > <https://groups.google.com/d/msgid/django-users/CAF1Wu3NkZCsU8oxLnuGPBtkWpPnq_L_H-o2dVb1rMUjm0pdW3A%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- Kind Regards. -------------------------------------------------- Chasan KIOUTSOUK MOUSTAFA, Freelance Software Engineer www.chasank.com -------------------------------------------------- -- You received this message because you are subscribed to the Google Groups "Django users" group. 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