PostgreSQL is designed to be easily extensible. For
this reason, extensions loaded into the database can function
just like features that are built in. The
contrib/
directory shipped with the source code
contains several extensions, which are described in
부록 F. Other extensions are developed
independently, like PostGIS. Even
PostgreSQL replication solutions can be developed
externally. For example, Slony-I is a popular
master/standby replication solution that is developed independently
from the core project.