diff options
Diffstat (limited to 'lib/python2.7/site-packages/django/db/models/expressions.py')
| -rw-r--r-- | lib/python2.7/site-packages/django/db/models/expressions.py | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/lib/python2.7/site-packages/django/db/models/expressions.py b/lib/python2.7/site-packages/django/db/models/expressions.py new file mode 100644 index 0000000..6e0f3c4 --- /dev/null +++ b/lib/python2.7/site-packages/django/db/models/expressions.py @@ -0,0 +1,186 @@ +import datetime + +from django.db.models.aggregates import refs_aggregate +from django.db.models.constants import LOOKUP_SEP +from django.utils import tree + +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 - note that these are generated by .bitand() + # and .bitor(), the '&' and '|' are reserved for boolean operator + # usage. + BITAND = '&' + BITOR = '|' + + 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 isinstance(other, datetime.timedelta): + return DateModifierNode([self, other], connector) + + 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 + + def contains_aggregate(self, existing_aggregates): + if self.children: + return any(child.contains_aggregate(existing_aggregates) + for child in self.children + if hasattr(child, 'contains_aggregate')) + else: + return refs_aggregate(self.name.split(LOOKUP_SEP), + existing_aggregates) + + def prepare_database_save(self, unused): + return self + + ################### + # 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 __truediv__(self, other): + return self._combine(other, self.DIV, False) + + def __div__(self, other): # Python 2 compatibility + return type(self).__truediv__(self, other) + + def __mod__(self, other): + return self._combine(other, self.MOD, False) + + def __and__(self, other): + raise NotImplementedError( + "Use .bitand() and .bitor() for bitwise logical operations." + ) + + def bitand(self, other): + return self._combine(other, self.BITAND, False) + + def __or__(self, other): + raise NotImplementedError( + "Use .bitand() and .bitor() for bitwise logical operations." + ) + + def bitor(self, other): + return self._combine(other, self.BITOR, 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 __rtruediv__(self, other): + return self._combine(other, self.DIV, True) + + def __rdiv__(self, other): # Python 2 compatibility + return type(self).__rtruediv__(self, other) + + def __rmod__(self, other): + return self._combine(other, self.MOD, True) + + def __rand__(self, other): + raise NotImplementedError( + "Use .bitand() and .bitor() for bitwise logical operations." + ) + + def __ror__(self, other): + raise NotImplementedError( + "Use .bitand() and .bitor() for bitwise logical operations." + ) + +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) + +class DateModifierNode(ExpressionNode): + """ + Node that implements the following syntax: + filter(end_date__gt=F('start_date') + datetime.timedelta(days=3, seconds=200)) + + which translates into: + POSTGRES: + WHERE end_date > (start_date + INTERVAL '3 days 200 seconds') + + MYSQL: + WHERE end_date > (start_date + INTERVAL '3 0:0:200:0' DAY_MICROSECOND) + + ORACLE: + WHERE end_date > (start_date + INTERVAL '3 00:03:20.000000' DAY(1) TO SECOND(6)) + + SQLITE: + WHERE end_date > django_format_dtdelta(start_date, "+" "3", "200", "0") + (A custom function is used in order to preserve six digits of fractional + second information on sqlite, and to format both date and datetime values.) + + Note that microsecond comparisons are not well supported with MySQL, since + MySQL does not store microsecond information. + + Only adding and subtracting timedeltas is supported, attempts to use other + operations raise a TypeError. + """ + def __init__(self, children, connector, negated=False): + if len(children) != 2: + raise TypeError('Must specify a node and a timedelta.') + if not isinstance(children[1], datetime.timedelta): + raise TypeError('Second child must be a timedelta.') + if connector not in (self.ADD, self.SUB): + raise TypeError('Connector must be + or -, not %s' % connector) + super(DateModifierNode, self).__init__(children, connector, negated) + + def evaluate(self, evaluator, qn, connection): + return evaluator.evaluate_date_modifier_node(self, qn, connection) |