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Refactored qs.add_q() and utils/tree.py
The sql/query.py add_q method did a lot of where/having tree hacking to get complex queries to work correctly. The logic was refactored so that it should be simpler to understand. The new logic should also produce leaner WHERE conditions. The changes cascade somewhat, as some other parts of Django (like add_filter() and WhereNode) expect boolean trees in certain format or they fail to work. So to fix the add_q() one must fix utils/tree.py, some things in add_filter(), WhereNode and so on. This commit also fixed add_filter to see negate clauses up the path. A query like .exclude(Q(reversefk__in=a_list)) didn't work similarly to .filter(~Q(reversefk__in=a_list)). The reason for this is that only the immediate parent negate clauses were seen by add_filter, and thus a tree like AND: (NOT AND: (AND: condition)) will not be handled correctly, as there is one intermediary AND node in the tree. The example tree is generated by .exclude(~Q(reversefk__in=a_list)). Still, aggregation lost connectors in OR cases, and F() objects and aggregates in same filter clause caused GROUP BY problems on some databases. Fixed #17600, fixed #13198, fixed #17025, fixed #17000, fixed #11293.
This commit is contained in:
Anssi Kääriäinen
@@ -19,14 +19,9 @@ class Node(object):
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"""
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Constructs a new Node. If no connector is given, the default will be
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used.
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Warning: You probably don't want to pass in the 'negated' parameter. It
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is NOT the same as constructing a node and calling negate() on the
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result.
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"""
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self.children = children and children[:] or []
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self.connector = connector or self.default
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self.subtree_parents = []
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self.negated = negated
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# We need this because of django.db.models.query_utils.Q. Q. __init__() is
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@@ -59,7 +54,6 @@ class Node(object):
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obj = Node(connector=self.connector, negated=self.negated)
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obj.__class__ = self.__class__
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obj.children = copy.deepcopy(self.children, memodict)
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obj.subtree_parents = copy.deepcopy(self.subtree_parents, memodict)
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return obj
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def __len__(self):
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@@ -83,74 +77,60 @@ class Node(object):
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"""
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return other in self.children
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def add(self, node, conn_type):
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def _prepare_data(self, data):
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"""
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Adds a new node to the tree. If the conn_type is the same as the root's
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current connector type, the node is added to the first level.
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Otherwise, the whole tree is pushed down one level and a new root
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connector is created, connecting the existing tree and the new node.
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A subclass hook for doing subclass specific transformations of the
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given data on combine() or add().
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"""
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if node in self.children and conn_type == self.connector:
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return
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if len(self.children) < 2:
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self.connector = conn_type
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return data
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def add(self, data, conn_type, squash=True):
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"""
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Combines this tree and the data represented by data using the
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connector conn_type. The combine is done by squashing the node other
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away if possible.
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This tree (self) will never be pushed to a child node of the
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combined tree, nor will the connector or negated properties change.
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The function returns a node which can be used in place of data
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regardless if the node other got squashed or not.
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If `squash` is False the data is prepared and added as a child to
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this tree without further logic.
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"""
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if data in self.children:
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return data
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data = self._prepare_data(data)
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if not squash:
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self.children.append(data)
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return data
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if self.connector == conn_type:
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if isinstance(node, Node) and (node.connector == conn_type or
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len(node) == 1):
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self.children.extend(node.children)
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# We can reuse self.children to append or squash the node other.
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if (isinstance(data, Node) and not data.negated
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and (data.connector == conn_type or len(data) == 1)):
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# We can squash the other node's children directly into this
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# node. We are just doing (AB)(CD) == (ABCD) here, with the
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# addition that if the length of the other node is 1 the
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# connector doesn't matter. However, for the len(self) == 1
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# case we don't want to do the squashing, as it would alter
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# self.connector.
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self.children.extend(data.children)
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return self
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else:
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self.children.append(node)
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# We could use perhaps additional logic here to see if some
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# children could be used for pushdown here.
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self.children.append(data)
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return data
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else:
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obj = self._new_instance(self.children, self.connector,
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self.negated)
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self.negated)
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self.connector = conn_type
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self.children = [obj, node]
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self.children = [obj, data]
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return data
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def negate(self):
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"""
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Negate the sense of the root connector. This reorganises the children
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so that the current node has a single child: a negated node containing
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all the previous children. This slightly odd construction makes adding
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new children behave more intuitively.
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Interpreting the meaning of this negate is up to client code. This
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method is useful for implementing "not" arrangements.
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Negate the sense of the root connector.
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"""
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self.children = [self._new_instance(self.children, self.connector,
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not self.negated)]
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self.connector = self.default
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def start_subtree(self, conn_type):
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"""
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Sets up internal state so that new nodes are added to a subtree of the
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current node. The conn_type specifies how the sub-tree is joined to the
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existing children.
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"""
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if len(self.children) == 1:
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self.connector = conn_type
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elif self.connector != conn_type:
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self.children = [self._new_instance(self.children, self.connector,
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self.negated)]
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self.connector = conn_type
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self.negated = False
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self.subtree_parents.append(self.__class__(self.children,
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self.connector, self.negated))
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self.connector = self.default
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self.negated = False
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self.children = []
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def end_subtree(self):
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"""
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Closes off the most recently unmatched start_subtree() call.
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This puts the current state into a node of the parent tree and returns
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the current instances state to be the parent.
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"""
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obj = self.subtree_parents.pop()
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node = self.__class__(self.children, self.connector)
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self.connector = obj.connector
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self.negated = obj.negated
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self.children = obj.children
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self.children.append(node)
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self.negated = not self.negated
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