In the previous post we configured three devuan servers from scratch using ansible adding the pgdg repository to the apt sources and installing the PostgreSQL binaries.
This tutorial will revisit the apt role’s configuration and will introduce a new role for configuring the postgres operating system’s user for passwordless ssh connections to each other server.
The ansible is a fictional device invented by Ursula K. Le Guin. The ansible allows fast communication between two points across the space, regardless of the distance.
It doesn’t surprise that the Red Hat’s ansible shares the same name as it gives a simple and efficient way to manage servers and automate tasks, yet remaining very lightweight with minimal requirements on the target machines.
In the previous post we introduced the PostgreSQL’s dependency system.
At first sight the implementation can look like a maze where the succession of relationships are not clear.
This post will try to give a practical example to show how pg_depend can act like an Ariadne’s thread in order to resolve the dependencies.
The scenario presented is very simple but can be used as a starting point for more complex requirements.
One of the things that distinguish PostgreSQL from other database systems is the way the dependencies between database objects are managed.
PostgreSQL do not allow any invalid object like views or functions. Therefore any action that can invalidate dependent objects results in an error or it’s propagated to the dependent objects.
The mechanism could be confusing at first sight. However the implementation is brilliant and gives great flexibility.
