/usr/share/pyshared/sqlalchemy/sql/operators.py is in python-sqlalchemy 0.7.4-1.
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# Copyright (C) 2005-2011 the SQLAlchemy authors and contributors <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Defines operators used in SQL expressions."""
from operator import (
and_, or_, inv, add, mul, sub, mod, truediv, lt, le, ne, gt, ge, eq, neg
)
# Py2K
from operator import (div,)
# end Py2K
from sqlalchemy.util import symbol
class Operators(object):
"""Base of comparison and logical operators.
Implements base methods :meth:`operate` and :meth:`reverse_operate`,
as well as :meth:`__and__`, :meth:`__or__`, :meth:`__invert__`.
Usually is used via its most common subclass
:class:`.ColumnOperators`.
"""
def __and__(self, other):
"""Implement the ``&`` operator.
When used with SQL expressions, results in an
AND operation, equivalent to
:func:`~.expression.and_`, that is::
a & b
is equivalent to::
from sqlalchemy import and_
and_(a, b)
Care should be taken when using ``&`` regarding
operator precedence; the ``&`` operator has the highest precedence.
The operands should be enclosed in parenthesis if they contain
further sub expressions::
(a == 2) & (b == 4)
"""
return self.operate(and_, other)
def __or__(self, other):
"""Implement the ``|`` operator.
When used with SQL expressions, results in an
OR operation, equivalent to
:func:`~.expression.or_`, that is::
a | b
is equivalent to::
from sqlalchemy import or_
or_(a, b)
Care should be taken when using ``|`` regarding
operator precedence; the ``|`` operator has the highest precedence.
The operands should be enclosed in parenthesis if they contain
further sub expressions::
(a == 2) | (b == 4)
"""
return self.operate(or_, other)
def __invert__(self):
"""Implement the ``~`` operator.
When used with SQL expressions, results in a
NOT operation, equivalent to
:func:`~.expression.not_`, that is::
~a
is equivalent to::
from sqlalchemy import not_
not_(a)
"""
return self.operate(inv)
def op(self, opstring):
"""produce a generic operator function.
e.g.::
somecolumn.op("*")(5)
produces::
somecolumn * 5
:param operator: a string which will be output as the infix operator
between this :class:`.ClauseElement` and the expression passed to the
generated function.
This function can also be used to make bitwise operators explicit. For
example::
somecolumn.op('&')(0xff)
is a bitwise AND of the value in somecolumn.
"""
def _op(b):
return self.operate(op, opstring, b)
return _op
def operate(self, op, *other, **kwargs):
"""Operate on an argument.
This is the lowest level of operation, raises
:class:`NotImplementedError` by default.
Overriding this on a subclass can allow common
behavior to be applied to all operations.
For example, overriding :class:`.ColumnOperators`
to apply ``func.lower()`` to the left and right
side::
class MyComparator(ColumnOperators):
def operate(self, op, other):
return op(func.lower(self), func.lower(other))
:param op: Operator callable.
:param \*other: the 'other' side of the operation. Will
be a single scalar for most operations.
:param \**kwargs: modifiers. These may be passed by special
operators such as :meth:`ColumnOperators.contains`.
"""
raise NotImplementedError(str(op))
def reverse_operate(self, op, other, **kwargs):
"""Reverse operate on an argument.
Usage is the same as :meth:`operate`.
"""
raise NotImplementedError(str(op))
class ColumnOperators(Operators):
"""Defines comparison and math operations.
By default all methods call down to
:meth:`Operators.operate` or :meth:`Operators.reverse_operate`
passing in the appropriate operator function from the
Python builtin ``operator`` module or
a SQLAlchemy-specific operator function from
:mod:`sqlalchemy.expression.operators`. For example
the ``__eq__`` function::
def __eq__(self, other):
return self.operate(operators.eq, other)
Where ``operators.eq`` is essentially::
def eq(a, b):
return a == b
A SQLAlchemy construct like :class:`.ColumnElement` ultimately
overrides :meth:`.Operators.operate` and others
to return further :class:`.ClauseElement` constructs,
so that the ``==`` operation above is replaced by a clause
construct.
The docstrings here will describe column-oriented
behavior of each operator. For ORM-based operators
on related objects and collections, see :class:`.RelationshipProperty.Comparator`.
"""
timetuple = None
"""Hack, allows datetime objects to be compared on the LHS."""
def __lt__(self, other):
"""Implement the ``<`` operator.
In a column context, produces the clause ``a < b``.
"""
return self.operate(lt, other)
def __le__(self, other):
"""Implement the ``<=`` operator.
In a column context, produces the clause ``a <= b``.
"""
return self.operate(le, other)
__hash__ = Operators.__hash__
def __eq__(self, other):
"""Implement the ``==`` operator.
In a column context, produces the clause ``a = b``.
If the target is ``None``, produces ``a IS NULL``.
"""
return self.operate(eq, other)
def __ne__(self, other):
"""Implement the ``!=`` operator.
In a column context, produces the clause ``a != b``.
If the target is ``None``, produces ``a IS NOT NULL``.
"""
return self.operate(ne, other)
def __gt__(self, other):
"""Implement the ``>`` operator.
In a column context, produces the clause ``a > b``.
"""
return self.operate(gt, other)
def __ge__(self, other):
"""Implement the ``>=`` operator.
In a column context, produces the clause ``a >= b``.
"""
return self.operate(ge, other)
def __neg__(self):
"""Implement the ``-`` operator.
In a column context, produces the clause ``-a``.
"""
return self.operate(neg)
def concat(self, other):
"""Implement the 'concat' operator.
In a column context, produces the clause ``a || b``,
or uses the ``concat()`` operator on MySQL.
"""
return self.operate(concat_op, other)
def like(self, other, escape=None):
"""Implement the ``like`` operator.
In a column context, produces the clause ``a LIKE other``.
"""
return self.operate(like_op, other, escape=escape)
def ilike(self, other, escape=None):
"""Implement the ``ilike`` operator.
In a column context, produces the clause ``a ILIKE other``.
"""
return self.operate(ilike_op, other, escape=escape)
def in_(self, other):
"""Implement the ``in`` operator.
In a column context, produces the clause ``a IN other``.
"other" may be a tuple/list of column expressions,
or a :func:`~.expression.select` construct.
"""
return self.operate(in_op, other)
def startswith(self, other, **kwargs):
"""Implement the ``startwith`` operator.
In a column context, produces the clause ``LIKE '<other>%'``
"""
return self.operate(startswith_op, other, **kwargs)
def endswith(self, other, **kwargs):
"""Implement the 'endswith' operator.
In a column context, produces the clause ``LIKE '%<other>'``
"""
return self.operate(endswith_op, other, **kwargs)
def contains(self, other, **kwargs):
"""Implement the 'contains' operator.
In a column context, produces the clause ``LIKE '%<other>%'``
"""
return self.operate(contains_op, other, **kwargs)
def match(self, other, **kwargs):
"""Implements the 'match' operator.
In a column context, this produces a MATCH clause, i.e.
``MATCH '<other>'``. The allowed contents of ``other``
are database backend specific.
"""
return self.operate(match_op, other, **kwargs)
def desc(self):
"""Produce a :func:`~.expression.desc` clause against the
parent object."""
return self.operate(desc_op)
def asc(self):
"""Produce a :func:`~.expression.asc` clause against the
parent object."""
return self.operate(asc_op)
def nullsfirst(self):
"""Produce a :func:`~.expression.nullsfirst` clause against the
parent object."""
return self.operate(nullsfirst_op)
def nullslast(self):
"""Produce a :func:`~.expression.nullslast` clause against the
parent object."""
return self.operate(nullslast_op)
def collate(self, collation):
"""Produce a :func:`~.expression.collate` clause against
the parent object, given the collation string."""
return self.operate(collate, collation)
def __radd__(self, other):
"""Implement the ``+`` operator in reverse.
See :meth:`__add__`.
"""
return self.reverse_operate(add, other)
def __rsub__(self, other):
"""Implement the ``-`` operator in reverse.
See :meth:`__sub__`.
"""
return self.reverse_operate(sub, other)
def __rmul__(self, other):
"""Implement the ``*`` operator in reverse.
See :meth:`__mul__`.
"""
return self.reverse_operate(mul, other)
def __rdiv__(self, other):
"""Implement the ``/`` operator in reverse.
See :meth:`__div__`.
"""
return self.reverse_operate(div, other)
def between(self, cleft, cright):
"""Produce a :func:`~.expression.between` clause against
the parent object, given the lower and upper range."""
return self.operate(between_op, cleft, cright)
def distinct(self):
"""Produce a :func:`~.expression.distinct` clause against the parent object."""
return self.operate(distinct_op)
def __add__(self, other):
"""Implement the ``+`` operator.
In a column context, produces the clause ``a + b``
if the parent object has non-string affinity.
If the parent object has a string affinity,
produces the concatenation operator, ``a || b`` -
see :meth:`concat`.
"""
return self.operate(add, other)
def __sub__(self, other):
"""Implement the ``-`` operator.
In a column context, produces the clause ``a - b``.
"""
return self.operate(sub, other)
def __mul__(self, other):
"""Implement the ``*`` operator.
In a column context, produces the clause ``a * b``.
"""
return self.operate(mul, other)
def __div__(self, other):
"""Implement the ``/`` operator.
In a column context, produces the clause ``a / b``.
"""
return self.operate(div, other)
def __mod__(self, other):
"""Implement the ``%`` operator.
In a column context, produces the clause ``a % b``.
"""
return self.operate(mod, other)
def __truediv__(self, other):
"""Implement the ``//`` operator.
In a column context, produces the clause ``a / b``.
"""
return self.operate(truediv, other)
def __rtruediv__(self, other):
"""Implement the ``//`` operator in reverse.
See :meth:`__truediv__`.
"""
return self.reverse_operate(truediv, other)
def from_():
raise NotImplementedError()
def as_():
raise NotImplementedError()
def exists():
raise NotImplementedError()
def is_(a, b):
return a.is_(b)
def isnot(a, b):
return a.isnot(b)
def collate(a, b):
return a.collate(b)
def op(a, opstring, b):
return a.op(opstring)(b)
def like_op(a, b, escape=None):
return a.like(b, escape=escape)
def notlike_op(a, b, escape=None):
raise NotImplementedError()
def ilike_op(a, b, escape=None):
return a.ilike(b, escape=escape)
def notilike_op(a, b, escape=None):
raise NotImplementedError()
def between_op(a, b, c):
return a.between(b, c)
def in_op(a, b):
return a.in_(b)
def notin_op(a, b):
raise NotImplementedError()
def distinct_op(a):
return a.distinct()
def startswith_op(a, b, escape=None):
return a.startswith(b, escape=escape)
def endswith_op(a, b, escape=None):
return a.endswith(b, escape=escape)
def contains_op(a, b, escape=None):
return a.contains(b, escape=escape)
def match_op(a, b):
return a.match(b)
def comma_op(a, b):
raise NotImplementedError()
def concat_op(a, b):
return a.concat(b)
def desc_op(a):
return a.desc()
def asc_op(a):
return a.asc()
def nullsfirst_op(a):
return a.nullsfirst()
def nullslast_op(a):
return a.nullslast()
_commutative = set([eq, ne, add, mul])
def is_commutative(op):
return op in _commutative
def is_ordering_modifier(op):
return op in (asc_op, desc_op,
nullsfirst_op, nullslast_op)
_associative = _commutative.union([concat_op, and_, or_])
_smallest = symbol('_smallest')
_largest = symbol('_largest')
_PRECEDENCE = {
from_: 15,
mul: 7,
truediv: 7,
# Py2K
div: 7,
# end Py2K
mod: 7,
neg: 7,
add: 6,
sub: 6,
concat_op: 6,
match_op: 6,
ilike_op: 5,
notilike_op: 5,
like_op: 5,
notlike_op: 5,
in_op: 5,
notin_op: 5,
is_: 5,
isnot: 5,
eq: 5,
ne: 5,
gt: 5,
lt: 5,
ge: 5,
le: 5,
between_op: 5,
distinct_op: 5,
inv: 5,
and_: 3,
or_: 2,
comma_op: -1,
collate: 7,
as_: -1,
exists: 0,
_smallest: -1000,
_largest: 1000
}
def is_precedent(operator, against):
if operator is against and operator in _associative:
return False
else:
return (_PRECEDENCE.get(operator, _PRECEDENCE[_smallest]) <=
_PRECEDENCE.get(against, _PRECEDENCE[_largest]))
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