As we all know that forum.xojo.com is an awesome place to find out more about Xojo and to ask questions. I am looking for something similar for PostgreSQL. Up until recently I have only been using the very outter level of its abilities and I am looking to go deeper. I would ask the questions here but they are not Xojo related in any form or fashion.
The main source of people answering questions about PostgreSQL are their mail lists (very active): https://www.postgresql.org/list/
(perhaps start with pgsql-general and pgsql-sql)