#35525: Django error with parsing JSONField
-------------------------------------+-------------------------------------
Reporter: Nirjal Paudel | Owner: nobody
Type: New feature | Status: closed
Component: Database layer | Version: dev
(models, ORM) |
Severity: Normal | Resolution: wontfix
Keywords: | Triage Stage:
Models,fields,encoding,decoding | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Nirjal Paudel):
Hi, thank-you for replying. Can you explain to me the `from_db_value`
part, as I think the default decoder option I mean just making an
exception for JSONField with json type and psycopg2. How about the two
code here. Sorry if this is stupid to ask
{{{
class DjangoJSONEncoder(json.JSONEncoder):
"""
JSONEncoder subclass that knows how to encode date/time, decimal
types, and
UUIDs.
"""
def default(self, o):
# See "Date Time String Format" in the ECMA-262 specification.
if isinstance(o, datetime.datetime):
r = o.isoformat()
if o.microsecond:
r = r[:23] + r[26:]
if r.endswith("+00:00"):
r = r.removesuffix("+00:00") + "Z"
return r
elif isinstance(o, datetime.date):
return o.isoformat()
elif isinstance(o, datetime.time):
if is_aware(o):
raise ValueError("JSON can't represent timezone-aware
times.")
r = o.isoformat()
if o.microsecond:
r = r[:12]
return r
elif isinstance(o, datetime.timedelta):
return duration_iso_string(o)
elif isinstance(o, (decimal.Decimal, uuid.UUID, Promise)):
return str(o)
# how about adding 2 conditions here
# one for list and dict to put it here
elif isinstance(o, list):
return o
elif isinstance(o, dict):
return o
else:
return super().default(o)
}}}
Replying to [comment:1 Simon Charette]:
> > So I had a django JSONField table with column called logs which is a
json field [ Not jsonb field ].
>
> Django doesn't support pointing fields designed to work with certain
database data types to others, `JSONField` is not exception.
>
> > Instead of doing this, why don't we check if the content/value parsed
from db is list or dict, by default python types for json
> > If yes - Don't do anything
> > If no and is a string instance - then perform json.loads() to it
>
> If you need this feature simply subclass `JSONField` and override it's
`from_db_value` method. Note that if you use this approach you won't be
able to implement support for the `decoder` option as this requires the
decoding to be performed by the field itself and not from psycopg.
--
Ticket URL: <https://code.djangoproject.com/ticket/35525#comment:2>
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