diff options
Diffstat (limited to 'lib/sqlalchemy/sql/operators.py')
| -rw-r--r-- | lib/sqlalchemy/sql/operators.py | 70 |
1 files changed, 65 insertions, 5 deletions
diff --git a/lib/sqlalchemy/sql/operators.py b/lib/sqlalchemy/sql/operators.py index 74eb73e46..8006d6145 100644 --- a/lib/sqlalchemy/sql/operators.py +++ b/lib/sqlalchemy/sql/operators.py @@ -31,6 +31,7 @@ from operator import rshift from operator import sub from operator import truediv +from .. import exc from .. import util @@ -117,7 +118,12 @@ class Operators: return self.operate(inv) def op( - self, opstring, precedence=0, is_comparison=False, return_type=None + self, + opstring, + precedence=0, + is_comparison=False, + return_type=None, + python_impl=None, ): """Produce a generic operator function. @@ -164,6 +170,26 @@ class Operators: :class:`.Boolean`, and those that do not will be of the same type as the left-hand operand. + :param python_impl: an optional Python function that can evaluate + two Python values in the same way as this operator works when + run on the database server. Useful for in-Python SQL expression + evaluation functions, such as for ORM hybrid attributes, and the + ORM "evaluator" used to match objects in a session after a multi-row + update or delete. + + e.g.:: + + >>> expr = column('x').op('+', python_impl=lambda a, b: a + b)('y') + + The operator for the above expression will also work for non-SQL + left and right objects:: + + >>> expr.operator(5, 10) + 15 + + .. versionadded:: 2.0 + + .. seealso:: :ref:`types_operators` @@ -171,14 +197,20 @@ class Operators: :ref:`relationship_custom_operator` """ - operator = custom_op(opstring, precedence, is_comparison, return_type) + operator = custom_op( + opstring, + precedence, + is_comparison, + return_type, + python_impl=python_impl, + ) def against(other): return operator(self, other) return against - def bool_op(self, opstring, precedence=0): + def bool_op(self, opstring, precedence=0, python_impl=None): """Return a custom boolean operator. This method is shorthand for calling @@ -191,7 +223,12 @@ class Operators: :meth:`.Operators.op` """ - return self.op(opstring, precedence=precedence, is_comparison=True) + return self.op( + opstring, + precedence=precedence, + is_comparison=True, + python_impl=python_impl, + ) def operate(self, op, *other, **kwargs): r"""Operate on an argument. @@ -219,6 +256,8 @@ class Operators: """ raise NotImplementedError(str(op)) + __sa_operate__ = operate + def reverse_operate(self, op, other, **kwargs): """Reverse operate on an argument. @@ -256,6 +295,16 @@ class custom_op: __name__ = "custom_op" + __slots__ = ( + "opstring", + "precedence", + "is_comparison", + "natural_self_precedent", + "eager_grouping", + "return_type", + "python_impl", + ) + def __init__( self, opstring, @@ -264,6 +313,7 @@ class custom_op: return_type=None, natural_self_precedent=False, eager_grouping=False, + python_impl=None, ): self.opstring = opstring self.precedence = precedence @@ -273,6 +323,7 @@ class custom_op: self.return_type = ( return_type._to_instance(return_type) if return_type else None ) + self.python_impl = python_impl def __eq__(self, other): return isinstance(other, custom_op) and other.opstring == self.opstring @@ -281,7 +332,16 @@ class custom_op: return id(self) def __call__(self, left, right, **kw): - return left.operate(self, right, **kw) + if hasattr(left, "__sa_operate__"): + return left.operate(self, right, **kw) + elif self.python_impl: + return self.python_impl(left, right, **kw) + else: + raise exc.InvalidRequestError( + f"Custom operator {self.opstring!r} can't be used with " + "plain Python objects unless it includes the " + "'python_impl' parameter." + ) class ColumnOperators(Operators): |