Redo the changes in [7773] in a better way.

This removes some of the leaky abstraction problems (lifting WhereNode
internals into the Query class) from that commit and makes it possible for
extensions to WhereNode to have access to the field instances. It's also
backwards-compatible with pre-[7773] code, which is also better.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7835 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/sql/query.py

@@ -1104,19 +1104,7 @@ class Query(object):
                 # that's harmless.
                 self.promote_alias(table)
 
-        # To save memory and copying time, convert the value from the Python
-        # object to the actual value used in the SQL query.
-        if field:
-            params = field.get_db_prep_lookup(lookup_type, value)
-        else:
-            params = Field().get_db_prep_lookup(lookup_type, value)
-        if isinstance(value, datetime.datetime):
-            annotation = datetime.datetime
-        else:
-            annotation = bool(value)
-
-        self.where.add((alias, col, field.db_type(), lookup_type, annotation,
-            params), connector)
+        self.where.add((alias, col, field, lookup_type, value), connector)
 
         if negate:
             for alias in join_list:
@@ -1126,8 +1114,8 @@ class Query(object):
                     for alias in join_list:
                         if self.alias_map[alias][JOIN_TYPE] == self.LOUTER:
                             j_col = self.alias_map[alias][RHS_JOIN_COL]
-                            entry = Node([(alias, j_col, None, 'isnull', True,
-                                    [True])])
+                            entry = self.where_class()
+                            entry.add((alias, j_col, None, 'isnull', True), AND)
                             entry.negate()
                             self.where.add(entry, AND)
                             break
@@ -1135,7 +1123,8 @@ class Query(object):
                     # Leaky abstraction artifact: We have to specifically
                     # exclude the "foo__in=[]" case from this handling, because
                     # it's short-circuited in the Where class.
-                    entry = Node([(alias, col, None, 'isnull', True, [True])])
+                    entry = self.where_class()
+                    entry.add((alias, col, None, 'isnull', True), AND)
                     entry.negate()
                     self.where.add(entry, AND)
 

django/db/models/sql/subqueries.py

@@ -49,7 +49,7 @@ class DeleteQuery(Query):
                 for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
                     where = self.where_class()
                     where.add((None, related.field.m2m_reverse_name(),
-                            related.field.db_type(), 'in', True,
+                            related.field, 'in',
                             pk_list[offset : offset+GET_ITERATOR_CHUNK_SIZE]),
                             AND)
                     self.do_query(related.field.m2m_db_table(), where)
@@ -59,11 +59,11 @@ class DeleteQuery(Query):
             if isinstance(f, generic.GenericRelation):
                 from django.contrib.contenttypes.models import ContentType
                 field = f.rel.to._meta.get_field(f.content_type_field_name)
-                w1.add((None, field.column, field.db_type(), 'exact', True,
-                        [ContentType.objects.get_for_model(cls).id]), AND)
+                w1.add((None, field.column, field, 'exact',
+                        ContentType.objects.get_for_model(cls).id), AND)
             for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
                 where = self.where_class()
-                where.add((None, f.m2m_column_name(), f.db_type(), 'in', True,
+                where.add((None, f.m2m_column_name(), f, 'in',
                         pk_list[offset : offset + GET_ITERATOR_CHUNK_SIZE]),
                         AND)
                 if w1:
@@ -81,7 +81,7 @@ class DeleteQuery(Query):
         for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
             where = self.where_class()
             field = self.model._meta.pk
-            where.add((None, field.column, field.db_type(), 'in', True,
+            where.add((None, field.column, field, 'in',
                     pk_list[offset : offset + GET_ITERATOR_CHUNK_SIZE]), AND)
             self.do_query(self.model._meta.db_table, where)
 
@@ -204,7 +204,7 @@ class UpdateQuery(Query):
         for offset in range(0, len(pk_list), GET_ITERATOR_CHUNK_SIZE):
             self.where = self.where_class()
             f = self.model._meta.pk
-            self.where.add((None, f.column, f.db_type(), 'in', True,
+            self.where.add((None, f.column, f, 'in',
                     pk_list[offset : offset + GET_ITERATOR_CHUNK_SIZE]),
                     AND)
             self.values = [(related_field.column, None, '%s')]

django/db/models/sql/where.py

@@ -27,7 +27,36 @@ class WhereNode(tree.Node):
     """
     default = AND
 
-    def as_sql(self, node=None, qn=None):
+    def add(self, data, connector):
+        """
+        Add a node to the where-tree. If the data is a list or tuple, it is
+        expected to be of the form (alias, col_name, field_obj, lookup_type,
+        value), which is then slightly munged before being stored (to avoid
+        storing any reference to field objects). Otherwise, the 'data' is
+        stored unchanged and can be anything with an 'as_sql()' method.
+        """
+        if not isinstance(data, (list, tuple)):
+            super(WhereNode, self).add(data, connector)
+            return
+
+        alias, col, field, lookup_type, value = data
+        if field:
+            params = field.get_db_prep_lookup(lookup_type, value)
+            db_type = field.db_type()
+        else:
+            # This is possible when we add a comparison to NULL sometimes (we
+            # don't really need to waste time looking up the associated field
+            # object).
+            params = Field().get_db_prep_lookup(lookup_type, value)
+            db_type = None
+        if isinstance(value, datetime.datetime):
+            annotation = datetime.datetime
+        else:
+            annotation = bool(value)
+        super(WhereNode, self).add((alias, col, db_type, lookup_type,
+                annotation, params), connector)
+
+    def as_sql(self, qn=None):
         """
         Returns the SQL version of the where clause and the value to be
         substituted in. Returns None, None if this node is empty.
@@ -36,60 +65,56 @@ class WhereNode(tree.Node):
         (generally not needed except by the internal implementation for
         recursion).
         """
-        if node is None:
-            node = self
         if not qn:
             qn = connection.ops.quote_name
-        if not node.children:
+        if not self.children:
             return None, []
         result = []
         result_params = []
         empty = True
-        for child in node.children:
+        for child in self.children:
             try:
                 if hasattr(child, 'as_sql'):
                     sql, params = child.as_sql(qn=qn)
-                    format = '(%s)'
-                elif isinstance(child, tree.Node):
-                    sql, params = self.as_sql(child, qn)
-                    if child.negated:
-                        format = 'NOT (%s)'
-                    elif len(child.children) == 1:
-                        format = '%s'
-                    else:
-                        format = '(%s)'
                 else:
+                    # A leaf node in the tree.
                     sql, params = self.make_atom(child, qn)
-                    format = '%s'
             except EmptyResultSet:
-                if node.connector == AND and not node.negated:
+                if self.connector == AND and not self.negated:
                     # We can bail out early in this particular case (only).
                     raise
-                elif node.negated:
+                elif self.negated:
                     empty = False
                 continue
             except FullResultSet:
                 if self.connector == OR:
-                    if node.negated:
+                    if self.negated:
                         empty = True
                         break
                     # We match everything. No need for any constraints.
                     return '', []
-                if node.negated:
+                if self.negated:
                     empty = True
                 continue
             empty = False
             if sql:
-                result.append(format % sql)
+                result.append(sql)
                 result_params.extend(params)
         if empty:
             raise EmptyResultSet
-        conn = ' %s ' % node.connector
-        return conn.join(result), result_params
+
+        conn = ' %s ' % self.connector
+        sql_string = conn.join(result)
+        if sql_string:
+            if self.negated:
+                sql_string = 'NOT (%s)' % sql_string
+            elif len(self.children) != 1:
+                sql_string = '(%s)' % sql_string
+        return sql_string, result_params
 
     def make_atom(self, child, qn):
         """
-        Turn a tuple (table_alias, field_name, db_type, lookup_type,
+        Turn a tuple (table_alias, column_name, db_type, lookup_type,
         value_annot, params) into valid SQL.
 
         Returns the string for the SQL fragment and the parameters to use for

django/utils/tree.py

@@ -29,6 +29,22 @@ class Node(object):
         self.subtree_parents = []
         self.negated = negated
 
+    # We need this because of django.db.models.query_utils.Q. Q. __init__() is
+    # problematic, but it is a natural Node subclass in all other respects.
+    def _new_instance(cls, children=None, connector=None, negated=False):
+        """
+        This is called to create a new instance of this class when we need new
+        Nodes (or subclasses) in the internal code in this class. Normally, it
+        just shadows __init__(). However, subclasses with an __init__ signature
+        that is not an extension of Node.__init__ might need to implement this
+        method to allow a Node to create a new instance of them (if they have
+        any extra setting up to do).
+        """
+        obj = Node(children, connector, negated)
+        obj.__class__ = cls
+        return obj
+    _new_instance = classmethod(_new_instance)
+
     def __str__(self):
         if self.negated:
             return '(NOT (%s: %s))' % (self.connector, ', '.join([str(c) for c
@@ -82,7 +98,8 @@ class Node(object):
             else:
                 self.children.append(node)
         else:
-            obj = Node(self.children, self.connector, self.negated)
+            obj = self._new_instance(self.children, self.connector,
+                    self.negated)
             self.connector = conn_type
             self.children = [obj, node]
 
@@ -96,7 +113,8 @@ class Node(object):
         Interpreting the meaning of this negate is up to client code. This
         method is useful for implementing "not" arrangements.
         """
-        self.children = [Node(self.children, self.connector, not self.negated)]
+        self.children = [self._new_instance(self.children, self.connector,
+                not self.negated)]
         self.connector = self.default
 
     def start_subtree(self, conn_type):
@@ -108,12 +126,13 @@ class Node(object):
         if len(self.children) == 1:
             self.connector = conn_type
         elif self.connector != conn_type:
-            self.children = [Node(self.children, self.connector, self.negated)]
+            self.children = [self._new_instance(self.children, self.connector,
+                    self.negated)]
             self.connector = conn_type
             self.negated = False
 
-        self.subtree_parents.append(Node(self.children, self.connector,
-                self.negated))
+        self.subtree_parents.append(self.__class__(self.children,
+                self.connector, self.negated))
         self.connector = self.default
         self.negated = False
         self.children = []
@@ -126,7 +145,7 @@ class Node(object):
         the current instances state to be the parent.
         """
         obj = self.subtree_parents.pop()
-        node = Node(self.children, self.connector)
+        node = self.__class__(self.children, self.connector)
         self.connector = obj.connector
         self.negated = obj.negated
         self.children = obj.children