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from datetime import datetime
from django.utils import tree
from django.utils.copycompat import deepcopy
class ExpressionNode(tree.Node):
"""
Base class for all query expressions.
"""
# Arithmetic connectors
ADD = '+'
SUB = '-'
MUL = '*'
DIV = '/'
MOD = '%%' # This is a quoted % operator - it is quoted
# because it can be used in strings that also
# have parameter substitution.
# Bitwise operators
AND = '&'
OR = '|'
def __init__(self, children=None, connector=None, negated=False):
if children is not None and len(children) > 1 and connector is None:
raise TypeError('You have to specify a connector.')
super(ExpressionNode, self).__init__(children, connector, negated)
def _combine(self, other, connector, reversed, node=None):
if reversed:
obj = ExpressionNode([other], connector)
obj.add(node or self, connector)
else:
obj = node or ExpressionNode([self], connector)
obj.add(other, connector)
return obj
###################
# VISITOR METHODS #
###################
def prepare(self, evaluator, query, allow_joins):
return evaluator.prepare_node(self, query, allow_joins)
def evaluate(self, evaluator, qn, connection):
return evaluator.evaluate_node(self, qn, connection)
#############
# OPERATORS #
#############
def __add__(self, other):
return self._combine(other, self.ADD, False)
def __sub__(self, other):
return self._combine(other, self.SUB, False)
def __mul__(self, other):
return self._combine(other, self.MUL, False)
def __div__(self, other):
return self._combine(other, self.DIV, False)
def __mod__(self, other):
return self._combine(other, self.MOD, False)
def __and__(self, other):
return self._combine(other, self.AND, False)
def __or__(self, other):
return self._combine(other, self.OR, False)
def __radd__(self, other):
return self._combine(other, self.ADD, True)
def __rsub__(self, other):
return self._combine(other, self.SUB, True)
def __rmul__(self, other):
return self._combine(other, self.MUL, True)
def __rdiv__(self, other):
return self._combine(other, self.DIV, True)
def __rmod__(self, other):
return self._combine(other, self.MOD, True)
def __rand__(self, other):
return self._combine(other, self.AND, True)
def __ror__(self, other):
return self._combine(other, self.OR, True)
def prepare_database_save(self, unused):
return self
class F(ExpressionNode):
"""
An expression representing the value of the given field.
"""
def __init__(self, name):
super(F, self).__init__(None, None, False)
self.name = name
def __deepcopy__(self, memodict):
obj = super(F, self).__deepcopy__(memodict)
obj.name = self.name
return obj
def prepare(self, evaluator, query, allow_joins):
return evaluator.prepare_leaf(self, query, allow_joins)
def evaluate(self, evaluator, qn, connection):
return evaluator.evaluate_leaf(self, qn, connection)
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