clarified minimum version required for MySQL backend (4.0.16)

Author: Richard Jones

doc/installation.txt

@@ -2,7 +2,7 @@
 Installing Roundup
 ==================
 
-:Version: $Revision: 1.64 $
+:Version: $Revision: 1.65 $
 
 .. contents::
 
@@ -242,12 +242,13 @@ There's several to choose from, each with benefits and limitations:
 **mysql**
   Backend for popular RDBMS MySQL. According to benchmarks, this backend works
   much faster than any of \*dbm ones, but slightly slower than metakit and
-  sqlite. For more info on backend installation see doc/mysql.txt. 
+  sqlite. You must read doc/mysql.txt for additional installation steps and
+  requirements.
 **postgresql**
   Backend for popular RDBMS PostgreSQL. According to benchmarks, this
   backend works much faster than any of \*dbm ones and mysql, but slightly
-  slower than metakit and sqlite.
-  For more info on backend installation see doc/postgresql.txt. 
+  slower than metakit and sqlite. You must read doc/postgresql.txt for
+  additional installation steps and requirements.
 **metakit**
   This backend is implemented over the metakit_ storage system, using Mk4Py as
   the interface. It scales much better than the dbm backends.

doc/mysql.txt

@@ -2,7 +2,7 @@
 MySQL Backend
 =============
 
-:version: $Revision: 1.6 $
+:version: $Revision: 1.7 $
 
 This notes detail the MySQL backend for the Roundup issue tracker.
 
@@ -13,9 +13,11 @@ Prerequisites
 To use MySQL as the backend for storing roundup data, you also need 
 to install:
 
-1. MySQL RDBMS 4.0 or higher - http://www.mysql.com. Your MySQL
+1. MySQL RDBMS 4.0.16 or higher - http://www.mysql.com. Your MySQL
    installation MUST support InnoDB tables (or Berkeley DB (BDB) tables
-   if you have no other choice)
+   if you have no other choice). If you're running < 4.0.16 (but not <4.0)
+   then you'll need to use BDB to pass all unit tests. Edit the
+   ``roundup/backends/back_mysql.py`` file to enable DBD instead of InnoDB.
 2. Python MySQL interface - http://sourceforge.net/projects/mysql-python
 
 :Note: the InnoDB implementation has a bug that Roundup tickles. See

roundup/backends/back_mysql.py

@@ -50,11 +50,10 @@ class Database(Database):
     arg = '%s'
 
     # Backend for MySQL to use.
-    # InnoDB is faster, but has a bug in its rollback machinery that causes
-    # some selects in subsequent transactions to fail. BDB does not have
-    # this bug, but is apparently much slower.
-    #mysql_backend = 'InnoDB'
-    mysql_backend = 'BDB'
+    # InnoDB is faster, but if you're running <4.0.16 then you'll need to
+    # use BDB to pass all unit tests.
+    mysql_backend = 'InnoDB'
+    #mysql_backend = 'BDB'
 
     def sql_open_connection(self):
         db = getattr(self.config, 'MYSQL_DATABASE')