Method validate

django/db/models/constraints.py:212–224

(self, model, instance, exclude=None, using=DEFAULT_DB_ALIAS)

        return schema_editor._delete_check_sql(model, self.name)

    def validate(self, model, instance, exclude=None, using=DEFAULT_DB_ALIAS):
        against = instance._get_field_expression_map(meta=model._meta, exclude=exclude)
        # Ignore constraints with excluded fields in condition.
        if exclude and self._expression_refs_exclude(model, self.condition, exclude):
            return
        condition = self.condition
        if connections[using].features.supports_comparing_boolean_expr:
            # Checks constraints do not fail when they evaluate to UNKNOWN.
            condition = Coalesce(condition, True, output_field=BooleanField())
        if not Q(condition).check(against, using=using):
            raise ValidationError(
                self.get_violation_error_message(), code=self.violation_error_code
            )

    def __repr__(self):
        return "<%s: condition=%s name=%s%s%s>" % (