"Julien Vallet" <julien(dot)vallet(at)density-tech(dot)com> writes:
> The result is "ERROR: UNION types text and bigint cannot be matched"
This is the identical issue reported here:
http://archives.postgresql.org/pgsql-bugs/2005-02/msg00008.php
See also this thread:
http://archives.postgresql.org/pgsql-general/2005-02/msg00693.php
The short answer is that what you wrote is illegal per the SQL spec
(which doesn't allow NULL to be used in ways where a type can't be
ascribed immediately). While we'd like to accept it, we have
not figured out a rule that doesn't break the spec in other ways.
For now I'd recommend casting the NULLs explicitly.
regards, tom lane