id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
32542	Native postgres json field support is broken	Artem	nobody	"In Django 3.1.1, there was a refactoring of encoders/decoders of DB fields which affected postgres json/jsonb field support.

Before:

Postgres **json** and **jsonb** field values are encoded/decoded into python native format by **psycopg2**. **JSONField** had it's own decoder but if was omitted if db has native json support.

After:

**Jsonb** field is no longer decoded by **psycopg2** (an empty stub is used instead of `json.joads`), all decoding stuff is delegated to `JSONField.from_db_value(...)`.
But postgres **json** field is still decoded by **psycopg2**, which causes 'TypeError' while trying to decode it again by `JSONField`.

Breaking commit: https://github.com/django/django/commit/0be51d2226fce030ac9ca840535a524f41e9832c

Example:

{{{
class CustomJSONField(models.JSONField):

    def db_type(self, *args, **kwargs):
        # stored as-is, keys order is preserved
        return 'json'

class TestModel(models.Model)
    json_data = CustomJSONField(default=dict)


TestModel(json_data={""foo"": ""bar""}).save()
TestModel.objects.last()
}}}


**Expected behavior:** code snippet works

**Actual behavior:** 
{{{
TypeError: the JSON object must be str, bytes or bytearray, not dict
}}}

The issue was mentioned in few tickets (#31973, #31956) but eventually their authors found workarounds (e.g. by switching to **jsonb** field) or still using Django <= 3.1. I think support of postgres json (not only jsonb) is important too.

The possible fix is to add the decoder stub for **json** field too:

Before (https://github.com/django/django/blob/main/django/db/backends/postgresql/base.py#L218):
{{{
psycopg2.extras.register_default_jsonb(conn_or_curs=connection, loads=lambda x: x)
}}}

After:

{{{
psycopg2.extras.register_default_json(conn_or_curs=connection, loads=lambda x: x)
psycopg2.extras.register_default_jsonb(conn_or_curs=connection, loads=lambda x: x)
}}}"	Bug	new	Database layer (models, ORM)	3.1	Normal				Unreviewed	1	0	0	0	0	0