Fixed .distinct() not working with slicing in Oracle, due to the

row numbers necessarily being distinct.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@9221 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/backends/oracle/query.py

@@ -26,8 +26,16 @@ def query_class(QueryClass, Database):
 
     class OracleQuery(QueryClass):
         def resolve_columns(self, row, fields=()):
-            index_start = len(self.extra_select.keys())
-            values = [self.convert_values(v, None) for v in row[:index_start]]
+            # If this query has limit/offset information, then we expect the
+            # first column to be an extra "_RN" column that we need to throw
+            # away.
+            if self.high_mark is not None or self.low_mark:
+                rn_offset = 1
+            else:
+                rn_offset = 0
+            index_start = rn_offset + len(self.extra_select.keys())
+            values = [self.convert_values(v, None)
+                      for v in row[rn_offset:index_start]]
             for value, field in map(None, row[index_start:], fields):
                 values.append(self.convert_values(value, field))
             return values
@@ -97,49 +105,17 @@ def query_class(QueryClass, Database):
                 sql, params = super(OracleQuery, self).as_sql(with_limits=False,
                         with_col_aliases=with_col_aliases)
             else:
-                # `get_columns` needs to be called before `get_ordering` to
-                # populate `_select_alias`.
-                self.pre_sql_setup()
-                self.get_columns()
-                ordering = self.get_ordering()
-
-                # Oracle's ROW_NUMBER() function requires an ORDER BY clause.
-                if ordering:
-                    rn_orderby = ', '.join(ordering)
-                else:
-                    # Create a default ORDER BY since none was specified.
-                    qn = self.quote_name_unless_alias
-                    opts = self.model._meta
-                    rn_orderby = '%s.%s' % (qn(opts.db_table),
-                        qn(opts.fields[0].db_column or opts.fields[0].column))
-
-                # Ensure the base query SELECTs our special "_RN" column
-                self.extra_select['_RN'] = ('ROW_NUMBER() OVER (ORDER BY %s)'
-                                            % rn_orderby, '')
                 sql, params = super(OracleQuery, self).as_sql(with_limits=False,
                                                         with_col_aliases=True)
 
                 # Wrap the base query in an outer SELECT * with boundaries on
                 # the "_RN" column.  This is the canonical way to emulate LIMIT
                 # and OFFSET on Oracle.
-                sql = 'SELECT * FROM (%s) WHERE "_RN" > %d' % (sql, self.low_mark)
+                sql = 'SELECT * FROM (SELECT ROW_NUMBER() OVER (ORDER BY 1) AS "_RN", "_SUB".* FROM (%s) "_SUB") WHERE "_RN" > %d' % (sql, self.low_mark)
                 if self.high_mark is not None:
                     sql = '%s AND "_RN" <= %d' % (sql, self.high_mark)
 
             return sql, params
 
-        def set_limits(self, low=None, high=None):
-            super(OracleQuery, self).set_limits(low, high)
-            # We need to select the row number for the LIMIT/OFFSET sql.
-            # A placeholder is added to extra_select now, because as_sql is
-            # too late to be modifying extra_select.  However, the actual sql
-            # depends on the ordering, so that is generated in as_sql.
-            self.extra_select['_RN'] = ('1', '')
-
-        def clear_limits(self):
-            super(OracleQuery, self).clear_limits()
-            if '_RN' in self.extra_select:
-                del self.extra_select['_RN']
-
     _classes[QueryClass] = OracleQuery
     return OracleQuery

tests/regressiontests/queries/models.py

@@ -334,6 +334,12 @@ Bug #4464
 >>> Item.objects.filter(tags__in=[t1, t2]).filter(tags=t3)
 [<Item: two>]
 
+Make sure .distinct() works with slicing (this was broken in Oracle).
+>>> Item.objects.filter(tags__in=[t1, t2]).order_by('name')[:3]
+[<Item: one>, <Item: one>, <Item: two>]
+>>> Item.objects.filter(tags__in=[t1, t2]).distinct().order_by('name')[:3]
+[<Item: one>, <Item: two>]
+
 Bug #2080, #3592
 >>> Author.objects.filter(item__name='one') | Author.objects.filter(name='a3')
 [<Author: a1>, <Author: a3>]