- The generated index name also is based on

a "max index name length" attribute which is
separate from the "max identifier length" -
this to appease MySQL who has a max length
of 64 for index names, separate from their
overall max length of 255.  [ticket:1412]

3 files changed, 17 insertions, 2 deletions

diff --git a/lib/sqlalchemy/dialects/mysql/base.py b/lib/sqlalchemy/dialects/mysql/base.py
index 1c61f47e1..a2d3748f3 100644
--- a/lib/sqlalchemy/dialects/mysql/base.py
+++ b/lib/sqlalchemy/dialects/mysql/base.py
@@ -1607,8 +1607,10 @@ class MySQLDialect(default.DefaultDialect):
     
     name = 'mysql'
     supports_alter = True
+    
     # identifiers are 64, however aliases can be 255...
     max_identifier_length = 255
+    max_index_name_length = 64
     
     supports_native_enum = True
     
diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index 0724d1fb9..390094c7d 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -59,7 +59,18 @@ class DefaultDialect(base.Dialect):
     # end Py2K
 
     name = 'default'
+    
+    # length at which to truncate
+    # any identifier.
     max_identifier_length = 9999
+    
+    # length at which to truncate
+    # the name of an index.
+    # Usually None to indicate
+    # 'use max_identifier_length'.
+    # thanks to MySQL, sigh
+    max_index_name_length = None
+    
     supports_sane_rowcount = True
     supports_sane_multi_rowcount = True
     dbapi_type_map = {}
diff --git a/lib/sqlalchemy/sql/compiler.py b/lib/sqlalchemy/sql/compiler.py
index 0383f9690..fcff5e355 100644
--- a/lib/sqlalchemy/sql/compiler.py
+++ b/lib/sqlalchemy/sql/compiler.py
@@ -1182,8 +1182,10 @@ class DDLCompiler(engine.Compiled):
 
     def _index_identifier(self, ident):
         if isinstance(ident, sql._generated_label):
-            if len(ident) > self.dialect.max_identifier_length:
-                return ident[0:self.dialect.max_identifier_length - 8] + \
+            max = self.dialect.max_index_name_length or \
+                        self.dialect.max_identifier_length
+            if len(ident) > max:
+                return ident[0:max - 8] + \
                                 "_" + util.md5_hex(ident)[-4:]
             else:
                 return ident