[melbourne-pug] Django: Best practice for importing data (was: Specify the database for a Django ModelForm instance)

[Ben Finney]

Mike Dewhirst <miked at dewhirst.com.au> writes:

> Can I ask why you are using manage.py to import csv data instead of a
> migration?

There are different scenarios when each makes sense.

* When the data import is conceptually a defining feature of the
  database (e.g. a collection of status values), and should exist from
  the first creation of the database, storing the data as a fixture is
  the best way.

  <URL:https://docs.djangoproject.com/en/1.10/howto/initial-data/>

  Use an initial data fixture when your database is just starting, and
  you know this data should exist in every new instance of the
  application.

* When the change in data is reflective of a change in the application
  behaviour (e.g. the application was only offering Country and State,
  but now needs to also offer City values), populating the new
  information with a migration is the right: the data should be there
  whenever the application behaviour aligns with that database state,
  and should not be there otherwise.

  <URL:https://docs.djangoproject.com/en/1.10/topics/migrations/#data-migrations>

  Use a migration when the change in data is required for every instance
  of the application which exists at that state of the program code.

* When the change in data does not represent any specific change in
  application behaviour (e.g. the application offered 135
  manually-entered products for sale, and now the owner wants to import
  another 6 000 additional products), a migration is too much hassle
  because there's no implied different behaviour of the application.

  <URL:https://docs.djangoproject.com/en/1.10/howto/custom-management-commands/>

  For small data additions, that do not need to be applied in every
  instance of the application, you could just use the application's user
  interface – or the Admin – to create them. But if the amount is large,
  a custom management command is best for automating it.

> I ask because I'm just starting to think about an upcoming csv (xlsx
> actually) import task of my own.

I hope that helps.

-- 
 \     “I was in the first submarine. Instead of a periscope, they had |
  `\               a kaleidoscope. ‘We're surrounded.’” —Steven Wright |
_o__)                                                                  |
Ben Finney