In TIBCO Spotfire version 10.10 and 11.4, you will not be able to see PostgreSQL functions listed in data sources that is set up using the Information designer tool.
This is due to a change in the handling of metadata in newer PostgreSQL .jar files, this has been fixed in TIBCO Spotfire Server 11.5.
There is a workaround that you can use that is outlined in this article:
https://community.tibco.com/wiki/tibco-spotfire-server-information-designer-fix-issues-postgresql-functions-not-showing-list