Class KeyTransform

django/db/models/fields/json.py:474–515

class KeyTransform(ProcessJSONLHSMixin, Transform):
    postgres_operator = "->"
    postgres_nested_operator = "#>"

    def __init__(self, key_name, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.key_name = str(key_name)

    def preprocess_lhs(self, compiler, connection):
        key_transforms = [self.key_name]
        previous = self.lhs
        while isinstance(previous, KeyTransform):
            key_transforms.insert(0, previous.key_name)
            previous = previous.lhs
        lhs, params = compiler.compile(previous)
        if connection.vendor == "oracle":
            # Escape string-formatting.
            key_transforms = [key.replace("%", "%%") for key in key_transforms]
        return lhs, params, key_transforms

    def as_mysql(self, compiler, connection):
        lhs, params, key_transforms = self.preprocess_lhs(compiler, connection)
        return self._process_as_mysql(lhs, params, connection, key_transforms)

    def as_oracle(self, compiler, connection):
        lhs, params, key_transforms = self.preprocess_lhs(compiler, connection)
        return self._process_as_oracle(lhs, params, connection, key_transforms)

    def as_postgresql(self, compiler, connection):
        lhs, params, key_transforms = self.preprocess_lhs(compiler, connection)
        if len(key_transforms) > 1:
            sql = "(%s %s %%s)" % (lhs, self.postgres_nested_operator)
            return sql, (*params, key_transforms)
        try:
            lookup = int(self.key_name)
        except ValueError:
            lookup = self.key_name
        return "(%s %s %%s)" % (lhs, self.postgres_operator), (*params, lookup)

    def as_sqlite(self, compiler, connection):
        lhs, params, key_transforms = self.preprocess_lhs(compiler, connection)
        return self._process_as_sqlite(lhs, params, connection, key_transforms)


class KeyTextTransform(KeyTransform):