The extensions described so far are all part of the PostgreSQL contrib package, which is shipped as part of the PostgreSQL source code. However, the packages you have seen are not the only ones available in the PostgreSQL community. There are many more packages that allow you to do all kinds of things.
Unfortunately, this chapter is too short to dig into all the stuff 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 ...
