Migrated issue, originally created by Anonymous

See discussion at http://groups.google.com/group/sqlalchemy/browse_thread/thread/5e51d180253cc14b

When first connecting to a database, SA issues a query to see if the DB returns unicode strings for certain data types using a CAST. Unfortunately, CAST was not added to MySQL until v 4.0.2, so SA 0.6.1 is unable to connect to older versions.

The mailing list discussion suggests 3 alternatives:

1. have cast() do nothing with the MySQL dialect if the MySQL version < 4.0.2 (is there some MySQL-specific syntax that works maybe ?)

2. have the MySQL dialect not run _check_unicode_returns if the version < 4.0.2

3. put the unicode checks in a try/except and default the returns to False if something didn't work

I've tested option 1 very briefly, and it seemed to work, but I have not tested extensively. I'm putting this ticket at low priority because I think I'm probably the only person still using such an old version, and I'm not going to have a chance to test further for a week or two at least.

The patch for turning CAST into a noop is:

diff --git a/lib/sqlalchemy/dialects/mysql/base.py b/lib/sqlalchemy/dialects/mysql/base.py
--- a/lib/sqlalchemy/dialects/mysql/base.py
+++ b/lib/sqlalchemy/dialects/mysql/base.py
@@ -1187,6 +1187,8 @@

     def visit_cast(self, cast, **kwargs):
         # No cast until 4, no decimals until 5.
+        if self.dialect.server_version_info < (4, 0, 2):
+            return self.process(cast.clause)
         type_ = self.process(cast.typeclause)
         if type_ is None:
             return self.process(cast.clause)

When I next get time to look at this, I'll add a patch for the tests to this ticket.

Thanks,

Simon