Connecting to external data sources with foreign data wrappers

Since PostgreSQL 9.1, one can use Foreign Data Wrappers (FDW) in order to connect to the external data sources that are then treated as they were local tables. More information can be found on the PostgreSQL wiki: https://wiki.postgresql.org/wiki/Foreign_data_wrappers.

Querying the external files or databases seems to be standard these days. But how about querying WFS services or OSM directly? Now, this sounds cool, doesn't it? You should certainly have a look at some of the clever GEO data wrappers:

• ogr_fdw: https://github.com/pramsey/pgsql-ogr-fdw
• osm_pbf_fdw: https://github.com/vpikulik/postgres_osm_pbf_fdw

In this example, we'll use ogr_fdw to connect to some external data sources. Starting with PostGIS 2.2, it is a part of the bundle and there is no need to install it as it should already be available.