Note: The following description applies both to Postgres-XC and PostgreSQL if not described explicitly.
In the sections that follow, we will discuss how you can extend the Postgres-XC SQL query language by adding:
functions (starting in Section 34.3)
aggregates (starting in Section 34.10)
data types (starting in Section 34.11)
operators (starting in Section 34.12)
operator classes for indexes (starting in Section 34.14)
packages of related objects (starting in Section 34.15)