Add a way to update multiple records at once

[Adrian Holovaty]

The Django ORM currently doesn't allow for the update of multiple records in a single statement. We can add this feature in a pretty clean and consistent way by adding a QuerySet.update() method:

# UPDATE place SET city='Chicago' WHERE city='chicago';
Place.objects.filter(city='chicago').update(city='Chicago')

# UPDATE contestant SET age=age+2 WHERE answer='1';
Contestant.objects.filter(answer='1').update(age=SqlClause('age+2'))

The second example introduces SqlClause, which would be a way of specifying clauses instead of hard-coded values. We could potentially begin using this SqlClause in other places, too.

[deepak <deep.thukral@…>]

need testing doing part1

[deepak <deep.thukral@…>]

Sorry, I was working on it before qs-rf tag, so I just added where i was till then. Its partial patch(covers example 1) and needs testing.

[James Bennett]

Duplicate of #4260.