PostgreSQL was designed from the start to be
extensible. For this reason, extensions loaded into the database can
function just like features that are packaged with the database. The
contrib/ directory shipped with the source code
contains a large number of extensions. The README file
in that directory contains a summary. They include conversion tools,
full-text indexing, XML tools, and additional data types
and indexing methods. Other extensions are developed independently,
like PostGIS. Even PostgreSQL
replication solutions are developed externally. For example,
Slony-I is a popular master/slave replication solution
that is developed independently from the core project.
There are several administration tools available for
PostgreSQL. The most popular is
pgAdmin, and there are several commercially
available ones.