Class DropConstraint

lib/sqlalchemy/sql/ddl.py:1162–1214

Represent an ALTER TABLE DROP CONSTRAINT statement.

class DropConstraint(_DropBase["Constraint"]):
    """Represent an ALTER TABLE DROP CONSTRAINT statement."""

    __visit_name__ = "drop_constraint"

    def __init__(
        self,
        element: Constraint,
        *,
        cascade: bool = False,
        if_exists: bool = False,
        isolate_from_table: bool | _NoArg = NO_ARG,
        **kw: Any,
    ) -> None:
        """Construct a new :class:`.DropConstraint` construct.

        :param element: a :class:`.Constraint` object

        :param cascade: optional boolean, indicates backend-specific
         "CASCADE CONSTRAINT" directive should be rendered if available

        :param if_exists: optional boolean, indicates backend-specific
         "IF EXISTS" directive should be rendered if available

        :param isolate_from_table: optional boolean. This is a deprecated
         setting that when ``True``, does the same thing that
         :paramref:`.AddConstraint.isolate_from_table` does, which is prevents
         the constraint from being associated with an inline ``CREATE TABLE``
         statement. It does not have any effect on the DROP process for a
         table and is an artifact of older SQLAlchemy versions,
         and will be removed in a future release.

         .. versionadded:: 2.0.39 - added
            :paramref:`.DropConstraint.isolate_from_table`, defaulting
            to True.  Previously, the behavior of this parameter was implicitly
            turned on in all cases.

         .. versionchanged:: 2.1 - This parameter has been deprecated and
            the default value of the flag was changed to ``False``.

        """
        self.cascade = cascade
        super().__init__(element, if_exists=if_exists, **kw)

        if isolate_from_table is not NO_ARG:
            util.warn_deprecated(
                "The ``isolate_from_table`` is deprecated and it be removed "
                "in a future release.",
                "2.1",
            )

            if isolate_from_table:
                element._create_rule = self._create_rule_disable


class SetTableComment(_CreateDropBase["Table"]):