django - update a queryset in a specific order -

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django - update a queryset in a specific order -

i have "index" field stores consequent range of integers, safety set unique.

now want increment field one, maintain unique update value in descending order:

mymodel.objects.all().order_by('-index').update(index=f('index')+1)

what surprises me on machine integrityerror gets raised , complains duplicated index value.

is there missed? save records 1 one?

thanks in advance!

update:

i think root problem there no order in sql update command (see update order by, , sql server: update table using order by)

obviously django translates statement sql update order_by, leads undefined behavior , creates different result per machine.

you ordering queryset ascending. can create descending adding '-' field name in order by:

mymodel.objects.all().order_by('-index').update(index=f('index')+1)

django docs order_by

django order django-queryset

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