For reference, traceback is here:  http://paste.pocoo.org/show/120779/

1) rdbms_common.Database.sql is supposed to work with Postgres and MySQL, I'm
just fixing it for the former.
2) Probably yes, but FWIW this patch fixes many other Postgres overflows in
hasnode: for superseder, status, etc.

I think we should fix this, then maybe refactor the DB code. I'm not sure
investing in refactoring and improving our own DB-compatibility layer is
desirable over picking an external ORM.