Fixed #19198 -- merged 4 different Oracle fixes

django/contrib/gis/tests/utils.py

@@ -26,7 +26,7 @@ mysql   = _default_db == 'mysql'
 spatialite = _default_db == 'spatialite'
 
 HAS_SPATIALREFSYS = True
-if oracle:
+if oracle and 'gis' in settings.DATABASES[DEFAULT_DB_ALIAS]['ENGINE']:
     from django.contrib.gis.db.backends.oracle.models import SpatialRefSys
 elif postgis:
     from django.contrib.gis.db.backends.postgis.models import SpatialRefSys

django/db/backends/oracle/base.py

@@ -256,6 +256,10 @@ WHEN (new.%(col_name)s IS NULL)
         if not name.startswith('"') and not name.endswith('"'):
             name = '"%s"' % util.truncate_name(name.upper(),
                                                self.max_name_length())
+        # Oracle puts the query text into a (query % args) construct, so % signs
+        # in names need to be escaped. The '%%' will be collapsed back to '%' at
+        # that stage so we aren't really making the name longer here.
+        name = name.replace('%','%%')
         return name.upper()
 
     def random_function_sql(self):

django/db/models/query.py

@@ -1418,8 +1418,15 @@ def get_cached_row(row, index_start, using,  klass_info, offset=0):
     fields = row[index_start : index_start + field_count]
     # If all the select_related columns are None, then the related
     # object must be non-existent - set the relation to None.
-    # Otherwise, construct the related object.
-    if fields == (None,) * field_count:
+    # Otherwise, construct the related object. Also, some backends treat ''
+    # and None equivalently for char fields, so we have to be prepared for
+    # '' values.
+    if connections[using].features.interprets_empty_strings_as_nulls:
+        vals = tuple([None if f == '' else f for f in fields])
+    else:
+        vals = fields
+
+    if vals == (None,) * field_count:
         obj = None
     else:
         if field_names: