Reconciling where- and having-clause behaviour.

Extricated the code that works directly with SQL columns (standard
"where" stuff) from the the code that takes SQL fragments and combines
it with lookup types and values. The latter portion is now more
generally reusable. Any existing code that was poking at Query.having
will now break in very visible ways (no subtle miscalculations, which is
a good thing).

This patch, en passant, removes the existing "having" test, since the
new implementation requires more setting up than previously. The
aggregates support (currently in a separate codebase) has tests for this
functionality that work as a replacement for the removed test.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@9700 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/sql/query.py

@@ -16,7 +16,7 @@ from django.db import connection
 from django.db.models import signals
 from django.db.models.fields import FieldDoesNotExist
 from django.db.models.query_utils import select_related_descend
-from django.db.models.sql.where import WhereNode, EverythingNode, AND, OR
+from django.db.models.sql.where import WhereNode, Constraint, EverythingNode, AND, OR
 from django.db.models.sql.datastructures import Count
 from django.core.exceptions import FieldError
 from datastructures import EmptyResultSet, Empty, MultiJoin
@@ -66,7 +66,7 @@ class BaseQuery(object):
         self.where = where()
         self.where_class = where
         self.group_by = []
-        self.having = []
+        self.having = where()
         self.order_by = []
         self.low_mark, self.high_mark = 0, None  # Used for offset/limit
         self.distinct = False
@@ -172,7 +172,7 @@ class BaseQuery(object):
         obj.where = deepcopy(self.where)
         obj.where_class = self.where_class
         obj.group_by = self.group_by[:]
-        obj.having = self.having[:]
+        obj.having = deepcopy(self.having)
         obj.order_by = self.order_by[:]
         obj.low_mark, obj.high_mark = self.low_mark, self.high_mark
         obj.distinct = self.distinct
@@ -261,7 +261,9 @@ class BaseQuery(object):
         # get_from_clause() for details.
         from_, f_params = self.get_from_clause()
 
-        where, w_params = self.where.as_sql(qn=self.quote_name_unless_alias)
+        qn = self.quote_name_unless_alias
+        where, w_params = self.where.as_sql(qn=qn)
+        having, h_params = self.having.as_sql(qn=qn)
         params = []
         for val in self.extra_select.itervalues():
             params.extend(val[1])
@@ -291,9 +293,8 @@ class BaseQuery(object):
             if not ordering:
                 ordering = self.connection.ops.force_no_ordering()
 
-        if self.having:
-            having, h_params = self.get_having()
-            result.append('HAVING %s' % ', '.join(having))
+        if having:
+            result.append('HAVING %s' % having)
             params.extend(h_params)
 
         if ordering:
@@ -577,24 +578,6 @@ class BaseQuery(object):
                 result.append(str(col))
         return result
 
-    def get_having(self):
-        """
-        Returns a tuple representing the SQL elements in the "having" clause.
-        By default, the elements of self.having have their as_sql() method
-        called or are returned unchanged (if they don't have an as_sql()
-        method).
-        """
-        result = []
-        params = []
-        for elt in self.having:
-            if hasattr(elt, 'as_sql'):
-                sql, params = elt.as_sql()
-                result.append(sql)
-                params.extend(params)
-            else:
-                result.append(elt)
-        return result, params
-
     def get_ordering(self):
         """
         Returns list representing the SQL elements in the "order by" clause.
@@ -1197,7 +1180,8 @@ class BaseQuery(object):
             self.promote_alias_chain(join_it, join_promote)
             self.promote_alias_chain(table_it, table_promote)
 
-        self.where.add((alias, col, field, lookup_type, value), connector)
+        self.where.add((Constraint(alias, col, field), lookup_type, value),
+            connector)
 
         if negate:
             self.promote_alias_chain(join_list)
@@ -1207,7 +1191,7 @@ class BaseQuery(object):
                         if self.alias_map[alias][JOIN_TYPE] == self.LOUTER:
                             j_col = self.alias_map[alias][RHS_JOIN_COL]
                             entry = self.where_class()
-                            entry.add((alias, j_col, None, 'isnull', True), AND)
+                            entry.add((Constraint(alias, j_col, None), 'isnull', True), AND)
                             entry.negate()
                             self.where.add(entry, AND)
                             break
@@ -1216,7 +1200,7 @@ class BaseQuery(object):
                     # exclude the "foo__in=[]" case from this handling, because
                     # it's short-circuited in the Where class.
                     entry = self.where_class()
-                    entry.add((alias, col, None, 'isnull', True), AND)
+                    entry.add((Constraint(alias, col, None), 'isnull', True), AND)
                     entry.negate()
                     self.where.add(entry, AND)