Ticket #9431: untitled 21.diff

Users/adam/Development/django/django/db/backends/mysql/validation.py

@@ -2 +2 @@
 
 class DatabaseValidation(BaseDatabaseValidation):
     def validate_field(self, errors, opts, f):
-        "Prior to MySQL 5.0.3, character fields could not exceed 255 characters"
+        """
+        Prior to MySQL 5.0.3 (i.e. MySQL 4.x), character fields could not exceed 255 characters
+        On all 5.0 MySQL and earlier, varchar fields cannot have more than 255 characters if the column
+        has a UNIQUE index and the table type is InnoDB.  MyISAM has some room for a few more characters 
+        but for the sake of portability, that will be ignored.
+        """"
         from django.db import models
         from django.db import connection
         db_version = connection.get_server_version()
@@ -10 +15 @@
             errors.add(opts,
                 '"%s": %s cannot have a "max_length" greater than 255 when you are using a version of MySQL prior to 5.0.3 (you are using %s).' % 
                 (f.name, f.__class__.__name__, '.'.join([str(n) for n in db_version[:3]])))
+        if isinstance(f, (models.CharField, models.CommaSeparatedIntegerField, models.SlugField)) and f.max_length > 255 and f.unique == True:
+            errors.add(opts,
+                '"%s": %s cannot have a "max_length" greater than 255 on a UNIQUE column when you are using MySQL (you are using %s).' % 
+                (f.name, f.__class__.__name__, '.'.join([str(n) for n in db_version[:3]])))
     
+ No newline at end of file