在 Django 1.9 中，使用 JSONField(本机 postgres jsonb)的约定是什么

The convention implied from the Django code seems to be to store null JSON values as NULL as opposed to as an empty string (as is the convention for the CharField). I say this because of the following:

empty_strings_allowed继承自CharField中的Field，设置为True:

django/db/models/fields/__init__.py#L96

class Field(RegisterLookupMixin):
    """Base class for all field types"""

    # Designates whether empty strings fundamentally are allowed at the
    # database level.
    empty_strings_allowed = True
    ...

JSONField, however, overrides it with False:

django/contrib/postgres/fields/jsonb.py#L13

class JSONField(Field):
    empty_strings_allowed = False
    ...

这会导致在实例化模型时，如果不显式传递这些字段的值，CharField默认为""，JSONField默认为None.

django/db/models/fields/init.py#L791

def get_default(self):
    """
    Returns the default value for this field.
    """
    if self.has_default():
        if callable(self.default):
            return self.default()
        return self.default
    if (not self.empty_strings_allowed or (self.null and
               not connection.features.interprets_empty_strings_as_nulls)):
        return None
    return ""

因此，如果你想 Select JSONField，你必须使用:

json_field = JSONField(blank=True, null=True)

如果您只使用blank=True，就像您在CharField中使用的那样，那么在try 运行MyModel.objects.create(...)而不显式传递json_field参数时，您将得到IntegrityError.