Fixed #10161 -- Modified evaluation of query expressions to allow for operators that take the form of functions. This is mostly for the benefit of Oracle, but it should prove useful later on. Thanks to Ian for the report and feedback on the fix.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@9898 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/backends/__init__.py

@@ -408,6 +408,15 @@ class BaseDatabaseOperations(object):
         """
         pass
 
+    def combine_expression(self, connector, sub_expressions):
+        """Combine a list of subexpressions into a single expression, using
+        the provided connecting operator. This is required because operators
+        can vary between backends (e.g., Oracle with %% and &) and between
+        subexpression types (e.g., date expressions)
+        """
+        conn = ' %s ' % connector
+        return conn.join(sub_expressions)
+
 class BaseDatabaseIntrospection(object):
     """
     This class encapsulates all backend-specific introspection utilities

django/db/backends/oracle/base.py

@@ -221,6 +221,16 @@ WHEN (new.%(col_name)s IS NULL)
         second = '%s-12-31'
         return [first % value, second % value]
 
+    def combine_expression(self, connector, sub_expressions):
+        "Oracle requires special cases for %% and & operators in query expressions"
+        if connector == '%%':
+            return 'MOD(%s)' % ','.join(sub_expressions)
+        elif connector == '&':
+            return 'BITAND(%s)' % ','.join(sub_expressions)
+        elif connector == '|':
+            raise NotImplementedError("Bit-wise or is not supported in Oracle.")
+        return super(DatabaseOperations, self).combine_expression(connector, sub_expressions)
+
 
 class DatabaseWrapper(BaseDatabaseWrapper):
 

django/db/models/sql/expressions.py

@@ -74,9 +74,8 @@ class SQLEvaluator(object):
             if sql:
                 expressions.append(format % sql)
                 expression_params.extend(params)
-        conn = ' %s ' % node.connector
 
-        return conn.join(expressions), expression_params
+        return connection.ops.combine_expression(node.connector, expressions), expression_params
 
     def evaluate_leaf(self, node, qn):
         if not qn:

tests/modeltests/expressions/models.py

@@ -37,14 +37,26 @@ __test__ = {'API_TESTS': """
 >>> Company(name='Test GmbH', num_employees=32, num_chairs=1,
 ...     ceo=Employee.objects.create(firstname='Max', lastname='Mustermann')).save()
 
+>>> company_query = Company.objects.values('name','num_employees','num_chairs').order_by('name','num_employees','num_chairs')
+
 # We can filter for companies where the number of employees is greater than the
 # number of chairs.
+>>> company_query.filter(num_employees__gt=F('num_chairs'))
+[{'num_chairs': 5, 'name': u'Example Inc.', 'num_employees': 2300}, {'num_chairs': 1, 'name': u'Test GmbH', 'num_employees': 32}]
 
->>> Company.objects.filter(num_employees__gt=F('num_chairs'))
-[<Company: Example Inc.>, <Company: Test GmbH>]
+# We can set one field to have the value of another field
+# Make sure we have enough chairs
+>>> _ = company_query.update(num_chairs=F('num_employees'))
+>>> company_query
+[{'num_chairs': 2300, 'name': u'Example Inc.', 'num_employees': 2300}, {'num_chairs': 3, 'name': u'Foobar Ltd.', 'num_employees': 3}, {'num_chairs': 32, 'name': u'Test GmbH', 'num_employees': 32}]
+
+# We can perform arithmetic operations in expressions
+# Make sure we have 2 spare chairs
+>>> _ =company_query.update(num_chairs=F('num_employees')+2)
+>>> company_query
+[{'num_chairs': 2302, 'name': u'Example Inc.', 'num_employees': 2300}, {'num_chairs': 5, 'name': u'Foobar Ltd.', 'num_employees': 3}, {'num_chairs': 34, 'name': u'Test GmbH', 'num_employees': 32}]
 
 # The relation of a foreign key can become copied over to an other foreign key.
-
 >>> Company.objects.update(point_of_contact=F('ceo'))
 3
 

tests/regressiontests/expressions_regress/models.py

@@ -1,7 +1,7 @@
 """
 Spanning tests for all the operations that F() expressions can perform.
 """
-
+from django.conf import settings
 from django.db import models
 
 #
@@ -87,11 +87,6 @@ Complex expressions of different connection types are possible.
 >>> Number.objects.get(pk=n.pk) # LH Bitwise ands on integers
 <Number: 40, 15.500>
 
->>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
->>> _ = Number.objects.filter(pk=n.pk).update(integer=F('integer') | 48)
->>> Number.objects.get(pk=n.pk) # LH Bitwise or on integers
-<Number: 58, 15.500>
-
 # Right hand operators
 
 >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
@@ -123,11 +118,20 @@ Complex expressions of different connection types are possible.
 >>> _ = Number.objects.filter(pk=n.pk).update(integer=15 & F('integer'))
 >>> Number.objects.get(pk=n.pk) # RH Bitwise ands on integers
 <Number: 10, 15.500>
+"""}
+
+# Oracle doesn't support the Bitwise OR operator.
+if settings.DATABASE_ENGINE != 'oracle':
+    __test__['API_TESTS'] += """
+
+>>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
+>>> _ = Number.objects.filter(pk=n.pk).update(integer=F('integer') | 48)
+>>> Number.objects.get(pk=n.pk) # LH Bitwise or on integers
+<Number: 58, 15.500>
 
 >>> _ = Number.objects.filter(pk=n.pk).update(integer=42, float=15.5)
 >>> _ = Number.objects.filter(pk=n.pk).update(integer=15 | F('integer'))
 >>> Number.objects.get(pk=n.pk) # RH Bitwise or on integers
 <Number: 47, 15.500>
 
-
-"""}
+"""