I just added the wonderful ajax marking block to our Moodle system. After little testing it seems that this block has some issues with our PostgreSQL backend.

In detail one of the major queries are aborting with the meaningful error message:

ERROR: failed to find conversion function from “unknown” to text

nice stuff :-)

It turns out that the usage of a “string as alias” are not handled correctly in postgresql, or so,… this part needs an explicit cast “::text”

If you also encountered this problem, you can download an updated query_base.class.php from -> here

have fun

Mario