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