I'm trying to migrate some value in Django, I'm using the Django model's When-Case
. My implementation is simple, it worked with static string:
When(
description__in=pre_desc,
then=Value("pre-string"),
),
When(
description__in=post_desc,
then=Value("some-post-string"),
)
This code above works. But the problem arises when I try to add something before or after to existing string:
pre_desc = ["a", "b", "c"]
post_desc = ["a", "b", "c"]
StoreO.objects.filter().update(
description=Case(
When(
description__in=pre_desc,
then=Value("pre-string" description),
),
When(
description__in=post_desc,
then=Value(description "some-post-string"),
),
default=Value("def_str")),
)
)
It says, description
is not defined. Can anyone give me some workaround?
I also tried str(F('description') 'randomstr')
which resulted in F('description') 'randomstr'
in the db.
CodePudding user response:
You reference a field with an F
expression [Django-doc], or here you concatenate the string with Concat
[Django-doc]:
from django.db.models.functions import Concat
pre_desc = ['a', 'b', 'c']
post_desc = ['a', 'b', 'c']
StoreO.objects.all().update(
description=Case(
When(
description__in=pre_desc,
then=Concat(Value('pre-string'), 'description'),
),
When(
description__in=post_desc,
then=Concat('description', Value('some-post-string')),
),
default=Value('def_str')),
)
)