The extensions that we have described so far are all part of the PostgreSQL contrib package, which is shipped as part of the PostgreSQL source code. However, the packages that we have seen are not the only ones available in the PostgreSQL community. There are many more packages that allow us to do all kinds of things.

Unfortunately, this chapter is too short to dig into everything that is currently out there. The number of modules is growing day by day and it is impossible to cover them all. Therefore, I only want to point out the ones I find the most important.

PostGIS (http://postgis.net/) is the Geographical Information Systems (GIS) database interface in the open source world. It has been adopted around the globe and is one of the de facto standards in the relational open source database world. It is a professional and extremely powerful solution.

If you are looking for geospatial routing, pgRouting is what you might be looking for. It offers various algorithms to find the best connections between locations and works on top of PostgreSQL.

In this chapter, we have already learned about the postgres_fdw extension, which allows us to connect to some other PostgreSQL databases. There are many more foreign data wrappers around. One of the most famous and most professional ones is the oracle_fdw extension. It allows you to integrate with Oracle and fetch data over the wire, as can be done with the postgres_fdw extension.

In some cases, you might also be interested in testing the stability of your infrastructure with pg_crash (https://github.com/cybertec-postgresql/pg_crash). The idea is to have a module that constantly crashes your database. pg_crash is an excellent choice for testing and debugging connection pools, and has the ability of an application to reconnect to a failing database. pg_crash will periodically run amok and kill database sessions or corrupt memory. It is ideal for long-term testing.