The desire to use database links has been around for many years already. However, around the turn of the century, PostgreSQL foreign data wrappers were not even on the horizon and a traditional database link implementation was definitely not in sight either. Around this time, a PostgreSQL developer from California (Joe Conway) pioneered work on database connectivity by introducing the concept of dblink into PostgreSQL. While dblink served people well over the years, it is no longer state of the art.
Therefore, it is recommended to move away from dblink to the more modern SQL/MED implementation (which is a specification that defines the way external data can be integrated in a relational database). The postgres_fdw ...
