Uninstallation of PostgreSQL
To uninstall PostgreSQL and all of its config files run
$ sudo pacman -Rcns postgresql
How to Install PostgreSQL on Arch-based Linux Distributions (Manjaro)
PostgreSQL (often called Postgres) is a free, open-source, and advanced relational database management system and is developed by The PostgreSQL Global Development Group. It is primarily written in the C Programming Language. In addition to SQL (relational) querying, Postgres also supports JSON (non-relational) querying.
This article is a step-by-step instruction for installing PostgreSQL on an Arch-based Linux system.