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582 lines
15 KiB
582 lines
15 KiB
# sql/operators.py
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# Copyright (C) 2005-2012 the SQLAlchemy authors and contributors <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""Defines operators used in SQL expressions."""
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from operator import (
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and_, or_, inv, add, mul, sub, mod, truediv, lt, le, ne, gt, ge, eq, neg
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)
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# Py2K
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from operator import (div,)
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# end Py2K
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from sqlalchemy.util import symbol
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class Operators(object):
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"""Base of comparison and logical operators.
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Implements base methods :meth:`operate` and :meth:`reverse_operate`,
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as well as :meth:`__and__`, :meth:`__or__`, :meth:`__invert__`.
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Usually is used via its most common subclass
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:class:`.ColumnOperators`.
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"""
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def __and__(self, other):
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"""Implement the ``&`` operator.
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When used with SQL expressions, results in an
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AND operation, equivalent to
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:func:`~.expression.and_`, that is::
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a & b
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is equivalent to::
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from sqlalchemy import and_
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and_(a, b)
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Care should be taken when using ``&`` regarding
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operator precedence; the ``&`` operator has the highest precedence.
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The operands should be enclosed in parenthesis if they contain
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further sub expressions::
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(a == 2) & (b == 4)
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"""
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return self.operate(and_, other)
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def __or__(self, other):
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"""Implement the ``|`` operator.
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When used with SQL expressions, results in an
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OR operation, equivalent to
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:func:`~.expression.or_`, that is::
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a | b
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is equivalent to::
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from sqlalchemy import or_
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or_(a, b)
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Care should be taken when using ``|`` regarding
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operator precedence; the ``|`` operator has the highest precedence.
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The operands should be enclosed in parenthesis if they contain
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further sub expressions::
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(a == 2) | (b == 4)
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"""
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return self.operate(or_, other)
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def __invert__(self):
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"""Implement the ``~`` operator.
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When used with SQL expressions, results in a
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NOT operation, equivalent to
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:func:`~.expression.not_`, that is::
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~a
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is equivalent to::
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from sqlalchemy import not_
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not_(a)
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"""
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return self.operate(inv)
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def op(self, opstring):
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"""produce a generic operator function.
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e.g.::
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somecolumn.op("*")(5)
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produces::
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somecolumn * 5
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:param operator: a string which will be output as the infix operator
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between this :class:`.ClauseElement` and the expression passed to the
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generated function.
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This function can also be used to make bitwise operators explicit. For
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example::
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somecolumn.op('&')(0xff)
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is a bitwise AND of the value in somecolumn.
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"""
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def _op(b):
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return self.operate(op, opstring, b)
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return _op
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def operate(self, op, *other, **kwargs):
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"""Operate on an argument.
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This is the lowest level of operation, raises
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:class:`NotImplementedError` by default.
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Overriding this on a subclass can allow common
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behavior to be applied to all operations.
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For example, overriding :class:`.ColumnOperators`
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to apply ``func.lower()`` to the left and right
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side::
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class MyComparator(ColumnOperators):
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def operate(self, op, other):
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return op(func.lower(self), func.lower(other))
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:param op: Operator callable.
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:param \*other: the 'other' side of the operation. Will
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be a single scalar for most operations.
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:param \**kwargs: modifiers. These may be passed by special
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operators such as :meth:`ColumnOperators.contains`.
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"""
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raise NotImplementedError(str(op))
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def reverse_operate(self, op, other, **kwargs):
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"""Reverse operate on an argument.
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Usage is the same as :meth:`operate`.
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"""
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raise NotImplementedError(str(op))
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class ColumnOperators(Operators):
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"""Defines comparison and math operations.
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By default all methods call down to
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:meth:`Operators.operate` or :meth:`Operators.reverse_operate`
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passing in the appropriate operator function from the
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Python builtin ``operator`` module or
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a SQLAlchemy-specific operator function from
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:mod:`sqlalchemy.expression.operators`. For example
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the ``__eq__`` function::
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def __eq__(self, other):
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return self.operate(operators.eq, other)
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Where ``operators.eq`` is essentially::
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def eq(a, b):
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return a == b
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A SQLAlchemy construct like :class:`.ColumnElement` ultimately
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overrides :meth:`.Operators.operate` and others
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to return further :class:`.ClauseElement` constructs,
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so that the ``==`` operation above is replaced by a clause
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construct.
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The docstrings here will describe column-oriented
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behavior of each operator. For ORM-based operators
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on related objects and collections, see :class:`.RelationshipProperty.Comparator`.
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"""
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timetuple = None
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"""Hack, allows datetime objects to be compared on the LHS."""
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def __lt__(self, other):
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"""Implement the ``<`` operator.
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In a column context, produces the clause ``a < b``.
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"""
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return self.operate(lt, other)
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def __le__(self, other):
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"""Implement the ``<=`` operator.
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In a column context, produces the clause ``a <= b``.
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"""
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return self.operate(le, other)
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__hash__ = Operators.__hash__
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def __eq__(self, other):
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"""Implement the ``==`` operator.
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In a column context, produces the clause ``a = b``.
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If the target is ``None``, produces ``a IS NULL``.
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"""
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return self.operate(eq, other)
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def __ne__(self, other):
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"""Implement the ``!=`` operator.
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In a column context, produces the clause ``a != b``.
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If the target is ``None``, produces ``a IS NOT NULL``.
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"""
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return self.operate(ne, other)
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def __gt__(self, other):
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"""Implement the ``>`` operator.
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In a column context, produces the clause ``a > b``.
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"""
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return self.operate(gt, other)
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def __ge__(self, other):
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"""Implement the ``>=`` operator.
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In a column context, produces the clause ``a >= b``.
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"""
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return self.operate(ge, other)
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def __neg__(self):
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"""Implement the ``-`` operator.
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In a column context, produces the clause ``-a``.
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"""
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return self.operate(neg)
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def concat(self, other):
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"""Implement the 'concat' operator.
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In a column context, produces the clause ``a || b``,
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or uses the ``concat()`` operator on MySQL.
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"""
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return self.operate(concat_op, other)
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def like(self, other, escape=None):
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"""Implement the ``like`` operator.
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In a column context, produces the clause ``a LIKE other``.
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"""
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return self.operate(like_op, other, escape=escape)
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def ilike(self, other, escape=None):
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"""Implement the ``ilike`` operator.
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In a column context, produces the clause ``a ILIKE other``.
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"""
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return self.operate(ilike_op, other, escape=escape)
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def in_(self, other):
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"""Implement the ``in`` operator.
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In a column context, produces the clause ``a IN other``.
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"other" may be a tuple/list of column expressions,
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or a :func:`~.expression.select` construct.
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"""
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return self.operate(in_op, other)
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def startswith(self, other, **kwargs):
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"""Implement the ``startwith`` operator.
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In a column context, produces the clause ``LIKE '<other>%'``
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"""
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return self.operate(startswith_op, other, **kwargs)
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def endswith(self, other, **kwargs):
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"""Implement the 'endswith' operator.
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In a column context, produces the clause ``LIKE '%<other>'``
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"""
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return self.operate(endswith_op, other, **kwargs)
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def contains(self, other, **kwargs):
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"""Implement the 'contains' operator.
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In a column context, produces the clause ``LIKE '%<other>%'``
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"""
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return self.operate(contains_op, other, **kwargs)
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def match(self, other, **kwargs):
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"""Implements the 'match' operator.
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In a column context, this produces a MATCH clause, i.e.
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``MATCH '<other>'``. The allowed contents of ``other``
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are database backend specific.
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"""
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return self.operate(match_op, other, **kwargs)
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def desc(self):
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"""Produce a :func:`~.expression.desc` clause against the
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parent object."""
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return self.operate(desc_op)
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def asc(self):
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"""Produce a :func:`~.expression.asc` clause against the
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parent object."""
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return self.operate(asc_op)
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def nullsfirst(self):
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"""Produce a :func:`~.expression.nullsfirst` clause against the
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parent object."""
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return self.operate(nullsfirst_op)
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def nullslast(self):
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"""Produce a :func:`~.expression.nullslast` clause against the
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parent object."""
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return self.operate(nullslast_op)
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def collate(self, collation):
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"""Produce a :func:`~.expression.collate` clause against
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the parent object, given the collation string."""
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return self.operate(collate, collation)
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def __radd__(self, other):
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"""Implement the ``+`` operator in reverse.
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See :meth:`__add__`.
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"""
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return self.reverse_operate(add, other)
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def __rsub__(self, other):
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"""Implement the ``-`` operator in reverse.
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See :meth:`__sub__`.
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"""
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return self.reverse_operate(sub, other)
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def __rmul__(self, other):
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"""Implement the ``*`` operator in reverse.
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See :meth:`__mul__`.
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"""
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return self.reverse_operate(mul, other)
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def __rdiv__(self, other):
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"""Implement the ``/`` operator in reverse.
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See :meth:`__div__`.
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"""
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return self.reverse_operate(div, other)
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def between(self, cleft, cright):
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"""Produce a :func:`~.expression.between` clause against
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the parent object, given the lower and upper range."""
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return self.operate(between_op, cleft, cright)
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def distinct(self):
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"""Produce a :func:`~.expression.distinct` clause against the parent object."""
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return self.operate(distinct_op)
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def __add__(self, other):
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"""Implement the ``+`` operator.
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In a column context, produces the clause ``a + b``
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if the parent object has non-string affinity.
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If the parent object has a string affinity,
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produces the concatenation operator, ``a || b`` -
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see :meth:`concat`.
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"""
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return self.operate(add, other)
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def __sub__(self, other):
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"""Implement the ``-`` operator.
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In a column context, produces the clause ``a - b``.
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"""
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return self.operate(sub, other)
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def __mul__(self, other):
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"""Implement the ``*`` operator.
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In a column context, produces the clause ``a * b``.
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"""
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return self.operate(mul, other)
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def __div__(self, other):
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"""Implement the ``/`` operator.
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In a column context, produces the clause ``a / b``.
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"""
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return self.operate(div, other)
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def __mod__(self, other):
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"""Implement the ``%`` operator.
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In a column context, produces the clause ``a % b``.
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"""
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return self.operate(mod, other)
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def __truediv__(self, other):
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"""Implement the ``//`` operator.
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In a column context, produces the clause ``a / b``.
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"""
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return self.operate(truediv, other)
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def __rtruediv__(self, other):
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"""Implement the ``//`` operator in reverse.
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See :meth:`__truediv__`.
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"""
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return self.reverse_operate(truediv, other)
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def from_():
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raise NotImplementedError()
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def as_():
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raise NotImplementedError()
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def exists():
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raise NotImplementedError()
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def is_(a, b):
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return a.is_(b)
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def isnot(a, b):
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return a.isnot(b)
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def collate(a, b):
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return a.collate(b)
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def op(a, opstring, b):
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return a.op(opstring)(b)
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def like_op(a, b, escape=None):
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return a.like(b, escape=escape)
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def notlike_op(a, b, escape=None):
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raise NotImplementedError()
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def ilike_op(a, b, escape=None):
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return a.ilike(b, escape=escape)
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def notilike_op(a, b, escape=None):
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raise NotImplementedError()
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def between_op(a, b, c):
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return a.between(b, c)
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def in_op(a, b):
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return a.in_(b)
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def notin_op(a, b):
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raise NotImplementedError()
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def distinct_op(a):
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return a.distinct()
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def startswith_op(a, b, escape=None):
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return a.startswith(b, escape=escape)
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def endswith_op(a, b, escape=None):
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return a.endswith(b, escape=escape)
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def contains_op(a, b, escape=None):
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return a.contains(b, escape=escape)
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def match_op(a, b):
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return a.match(b)
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def comma_op(a, b):
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raise NotImplementedError()
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def concat_op(a, b):
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return a.concat(b)
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def desc_op(a):
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return a.desc()
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def asc_op(a):
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return a.asc()
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def nullsfirst_op(a):
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return a.nullsfirst()
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def nullslast_op(a):
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return a.nullslast()
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_commutative = set([eq, ne, add, mul])
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def is_commutative(op):
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return op in _commutative
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def is_ordering_modifier(op):
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return op in (asc_op, desc_op,
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nullsfirst_op, nullslast_op)
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_associative = _commutative.union([concat_op, and_, or_])
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_smallest = symbol('_smallest')
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_largest = symbol('_largest')
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_PRECEDENCE = {
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from_: 15,
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mul: 7,
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truediv: 7,
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# Py2K
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div: 7,
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# end Py2K
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mod: 7,
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neg: 7,
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add: 6,
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sub: 6,
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concat_op: 6,
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match_op: 6,
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ilike_op: 5,
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notilike_op: 5,
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like_op: 5,
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notlike_op: 5,
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in_op: 5,
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notin_op: 5,
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is_: 5,
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isnot: 5,
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eq: 5,
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ne: 5,
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gt: 5,
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lt: 5,
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ge: 5,
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le: 5,
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between_op: 5,
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distinct_op: 5,
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inv: 5,
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and_: 3,
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or_: 2,
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comma_op: -1,
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collate: 7,
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as_: -1,
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exists: 0,
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_smallest: -1000,
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_largest: 1000
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}
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def is_precedent(operator, against):
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if operator is against and operator in _associative:
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return False
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else:
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return (_PRECEDENCE.get(operator, _PRECEDENCE[_smallest]) <=
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_PRECEDENCE.get(against, _PRECEDENCE[_largest]))
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