JSONField() does not save properly when nested as a child of ArrayField()

Question

Straightforward question: setting a field as ArrayField(JSONField(...),...) using Django 1.9+ and PostgreSQL 9.4.6 does not work when saving

# models.py
class Foo(models.Model):
    bar = ArrayField(JSONField(blank=True, null=True), default=list([]))

# app.py
...
data = request.data #ie. [{...}, {...}] 
# variations that were tested:
# JSON.stringify([{...}, {...}, ...])
# JSON.stringify([JSON.stringify({...}), JSON.stringify({...}), ...]
# any mix of non-JSON.stringified and stringified objects being sent via AJAX

Foo(bar=data)

# error message:
django.db.utils.ProgrammingError: column "bar" is of type \
jsonb[] but expression is of type text[]
LINE 1: INSERT INTO "app_foo" ("bar") VALUES (ARRAY['{"name": ...
                                                ^
HINT:  You will need to rewrite or cast the expression.

have you tried Foo(fooField=data) where data is a dictionary rather than a string? IE Foo(fooField=json.loads(request.data))? — Hamms
– Hamms, Commented Mar 28, 2016 at 21:50
@Hamms I get this error: TypeError: the JSON object must be str, not 'list' ...which begs the question, if JSON has to be 'str', then it can't possibly be jsonb[] even when saved properly (it will always be text[]) — imdaveho
– imdaveho, Commented Mar 28, 2016 at 21:53
@Hamms I'm trying to save an Array of JSON objects...not a single JSON object, so that won't make sense. — imdaveho
– imdaveho, Commented Mar 28, 2016 at 21:58
@jDo you're right, if you could just post an answer mirroring mine below I'll use it as the default answer so you can get some points (I'm an SO newb, so I'll gladly give credit where credit is due) — imdaveho
– imdaveho, Commented Mar 28, 2016 at 22:25

Pang · Accepted Answer · 2016-03-30 00:51:18Z

5

@jDO it seems your comment is correct. There is no need to nest JSONField in ArrayField as JSONField supports lists. Here is the updated code:

# models.py
class Foo(models.Model):
    bar = JSONField(default=list([]))

# app.py
...
data = request.data #ie. [{...}, {...}] 
Foo(bar=data)

# works!

edited Mar 30, 2016 at 0:51

Pang

10.2k146 gold badges87 silver badges126 bronze badges

answered Mar 28, 2016 at 22:24

imdaveho

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2 Comments

Jose Jorge Lorenzo Vila Over a year ago

I wonder if there are limitations/benefits in the kind of queries we can use if we use: JSONField(default=list) vs ArrayField(JSONField())

Seb D. Over a year ago

@JoseJorgeLorenzoVila: yes there are. For instance you can filter on the length of ArrayField, like .filter(bar__len=1), but not on JSONField. For that reason, this is unfortunate that we cannot nest json on array, since it's not equivalent to a simple json field. (But anyway it's probably the sign that a better design is needed).

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