import operator
from sqlalchemy.sql import operators,functions
from sqlalchemy.sql import expression
class UnevaluatableError(Exception):
pass
_straight_ops = set(getattr(operators, op)
for op in ('add', 'mul', 'sub',
# Py2K
'div',
# end Py2K
'mod', 'truediv',
'lt', 'le', 'ne', 'gt', 'ge', 'eq'))
_notimplemented_ops = set(getattr(operators, op)
for op in ('like_op', 'notlike_op', 'ilike_op',
'notilike_op', 'between_op', 'in_op',
'notin_op', 'endswith_op', 'concat_op'))
class EvaluatorCompiler(object):
def process(self, clause):
meth = getattr(self, "visit_%s" % clause.__visit_name__, None)
if not meth:
raise UnevaluatableError("Cannot evaluate %s" % type(clause).__name__)
return meth(clause)
def visit_grouping(self, clause):
return self.process(clause.element)
def visit_null(self, clause):
return lambda obj: None
def visit_column(self, clause):
if 'parentmapper' in clause._annotations:
key = clause._annotations['parentmapper']._get_col_to_prop(clause).key
else:
key = clause.key
get_corresponding_attr = operator.attrgetter(key)
return lambda obj: get_corresponding_attr(obj)
def visit_clauselist(self, clause):
evaluators = map(self.process, clause.clauses)
if clause.operator is operators.or_:
def evaluate(obj):
has_null = False
for sub_evaluate in evaluators:
value = sub_evaluate(obj)
if value:
return True
has_null = has_null or value is None
if has_null:
return None
return False
elif clause.operator is operators.and_:
def evaluate(obj):
for sub_evaluate in evaluators:
value = sub_evaluate(obj)
if not value:
if value is None:
return None
return False
return True
else:
raise UnevaluatableError("Cannot evaluate clauselist with operator %s" % clause.operator)
return evaluate
def visit_binary(self, clause):
eval_left,eval_right = map(self.process, [clause.left, clause.right])
operator = clause.operator
if operator is operators.is_:
def evaluate(obj):
return eval_left(obj) == eval_right(obj)
elif operator is operators.isnot:
def evaluate(obj):
return eval_left(obj) != eval_right(obj)
elif operator in _straight_ops:
def evaluate(obj):
left_val = eval_left(obj)
right_val = eval_right(obj)
if left_val is None or right_val is None:
return None
return operator(eval_left(obj), eval_right(obj))
else:
raise UnevaluatableError("Cannot evaluate %s with operator %s" % (type(clause).__name__, clause.operator))
return evaluate
def visit_unary(self, clause):
eval_inner = self.process(clause.element)
if clause.operator is operators.inv:
def evaluate(obj):
value = eval_inner(obj)
if value is None:
return None
return not value
return evaluate
raise UnevaluatableError("Cannot evaluate %s with operator %s" % (type(clause).__name__, clause.operator))
def visit_bindparam(self, clause):
val = clause.value
return lambda obj: val
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