Fixed #12977 -- Ensure that indexes don't exceed character limits on …

…MySQL. Thanks to carljm for the original report, and hgeerts@osso.nl for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@13040 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/backends/creation.py

@@ -260,6 +260,8 @@ def sql_indexes_for_model(self, model, style):
 
     def sql_indexes_for_field(self, model, f, style):
         "Return the CREATE INDEX SQL statements for a single model field"
+        from django.db.backends.util import truncate_name
+
         if f.db_index and not f.unique:
             qn = self.connection.ops.quote_name
             tablespace = f.db_tablespace or model._meta.db_tablespace
@@ -271,8 +273,9 @@ def sql_indexes_for_field(self, model, f, style):
                     tablespace_sql = ''
             else:
                 tablespace_sql = ''
+            i_name = '%s_%s' % (model._meta.db_table, self._digest(f.column))
             output = [style.SQL_KEYWORD('CREATE INDEX') + ' ' +
-                style.SQL_TABLE(qn('%s_%s' % (model._meta.db_table, f.column))) + ' ' +
+                style.SQL_TABLE(qn(truncate_name(i_name, self.connection.ops.max_name_length()))) + ' ' +
                 style.SQL_KEYWORD('ON') + ' ' +
                 style.SQL_TABLE(qn(model._meta.db_table)) + ' ' +
                 "(%s)" % style.SQL_FIELD(qn(f.column)) +

django/db/backends/mysql/base.py

@@ -227,6 +227,9 @@ def year_lookup_bounds(self, value):
         second = '%s-12-31 23:59:59.99'
         return [first % value, second % value]
 
+    def max_name_length(self):
+        return 64
+
 class DatabaseWrapper(BaseDatabaseWrapper):
 
     operators = {