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 35149 JSONField db_default requires wrapping values in json.dumps() David Sanders Simon Charette "This caught me out as I was expecting `db_default` to accept the same types as what would be set on model instance fields. **tl;dr** This will cause psycopg to raise `ProgrammingError: cannot adapt type 'dict'` {{{ class Foo(models.Model): json = models.JSONField(db_default={""foo"": ""bar""}) }}} however this works: {{{ class Foo(models.Model): json = models.JSONField(db_default=json.dumps({""foo"": ""bar""})) }}} At the very least this may be a doc update but I feel like it violates principle of least astonishment to not use the same type that JSONField attrs use. If we do decide to make this consistent it seems like `BaseSchemaEditor.db_default_sql()` [1] just needs to be aware of the field's type and adapt it correctly – something like calling `get_db_prep_value()`? [1] https://github.com/django/django/blob/2005530920e7c290bb1cf7d9ada155250faa81ad/django/db/backends/base/schema.py#L411 **Further details** Migration generated without json.dumps: {{{ class Migration(migrations.Migration): initial = True dependencies = [] operations = [ migrations.CreateModel( name=""Foo"", fields=[ ( ""id"", models.BigAutoField( auto_created=True, primary_key=True, serialize=False, verbose_name=""ID"", ), ), (""json"", models.JSONField(db_default=models.Value({""foo"": ""bar""}))), ], ), ] }}} Traceback when applying above migration: {{{ django-sample % dj migrate jsonfield_dbdefault Operations to perform: Apply all migrations: jsonfield_dbdefault Running migrations: Applying jsonfield_dbdefault.0001_initial...Traceback (most recent call last): File ""/path/to/projects/django-sample/./manage.py"", line 22, in main() File ""/path/to/projects/django-sample/./manage.py"", line 18, in main execute_from_command_line(sys.argv) File ""/path/to/projects/django/django/core/management/__init__.py"", line 442, in execute_from_command_line utility.execute() File ""/path/to/projects/django/django/core/management/__init__.py"", line 436, in execute self.fetch_command(subcommand).run_from_argv(self.argv) File ""/path/to/projects/django/django/core/management/base.py"", line 413, in run_from_argv self.execute(*args, **cmd_options) File ""/path/to/projects/django/django/core/management/base.py"", line 459, in execute output = self.handle(*args, **options) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django/django/core/management/base.py"", line 107, in wrapper res = handle_func(*args, **kwargs) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django/django/core/management/commands/migrate.py"", line 356, in handle post_migrate_state = executor.migrate( ^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django/django/db/migrations/executor.py"", line 135, in migrate state = self._migrate_all_forwards( ^^^^^^^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django/django/db/migrations/executor.py"", line 167, in _migrate_all_forwards state = self.apply_migration( ^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django/django/db/migrations/executor.py"", line 252, in apply_migration state = migration.apply(state, schema_editor) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django/django/db/migrations/migration.py"", line 132, in apply operation.database_forwards( File ""/path/to/projects/django/django/db/migrations/operations/models.py"", line 97, in database_forwards schema_editor.create_model(model) File ""/path/to/projects/django/django/db/backends/base/schema.py"", line 485, in create_model self.execute(sql, params or None) File ""/path/to/projects/django/django/db/backends/postgresql/schema.py"", line 46, in execute sql = self.connection.ops.compose_sql(str(sql), params) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django/django/db/backends/postgresql/operations.py"", line 193, in compose_sql return mogrify(sql, params, self.connection) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django/django/db/backends/postgresql/psycopg_any.py"", line 22, in mogrify return ClientCursor(cursor.connection).mogrify(sql, params) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django-sample/.direnv/python-3.11/lib/python3.11/site-packages/psycopg/client_cursor.py"", line 40, in mogrify pgq = self._convert_query(query, params) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django-sample/.direnv/python-3.11/lib/python3.11/site-packages/psycopg/client_cursor.py"", line 79, in _convert_query pgq.convert(query, params) File ""/path/to/projects/django-sample/.direnv/python-3.11/lib/python3.11/site-packages/psycopg/_queries.py"", line 213, in convert self.dump(vars) File ""/path/to/projects/django-sample/.direnv/python-3.11/lib/python3.11/site-packages/psycopg/_queries.py"", line 223, in dump self.params = tuple( ^^^^^^ File ""/path/to/projects/django-sample/.direnv/python-3.11/lib/python3.11/site-packages/psycopg/_queries.py"", line 224, in self._tx.as_literal(p) if p is not None else b""NULL"" for p in params ^^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django-sample/.direnv/python-3.11/lib/python3.11/site-packages/psycopg/_transform.py"", line 198, in as_literal dumper = self.get_dumper(obj, PY_TEXT) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django-sample/.direnv/python-3.11/lib/python3.11/site-packages/psycopg/_transform.py"", line 245, in get_dumper raise ex from None File ""/path/to/projects/django-sample/.direnv/python-3.11/lib/python3.11/site-packages/psycopg/_transform.py"", line 243, in get_dumper dcls = self.adapters.get_dumper(key, format) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ File ""/path/to/projects/django-sample/.direnv/python-3.11/lib/python3.11/site-packages/psycopg/_adapters_map.py"", line 223, in get_dumper raise e.ProgrammingError( psycopg.ProgrammingError: cannot adapt type 'dict' using placeholder '%t' (format: TEXT) }}}" Bug closed Database layer (models, ORM) 5.0 Release blocker fixed JSONField db_default Simon Charette Lily Foote Carlton Gibson Ready for checkin 1 0 0 0 0 0