Book Image

Mastering PostgreSQL 9.6

By : Hans-Jürgen Schönig
Book Image

Mastering PostgreSQL 9.6

By: Hans-Jürgen Schönig

Overview of this book

PostgreSQL is an open source database used for handling large datasets (Big Data) and as a JSON document database. It also has applications in the software and web domains. This book will enable you to build better PostgreSQL applications and administer databases more efficiently. We begin by explaining the advanced database design concepts in PostgreSQL 9.6, along with indexing and query optimization. You will also see how to work with event triggers and perform concurrent transactions and table partitioning, along with exploring SQL and server tuning. We will walk you through implementing advanced administrative tasks such as server maintenance and monitoring, replication, recovery and high availability, and much more. You will understand the common and not-so-common troubleshooting problems and how you can overcome them. By the end of this book, you will have an expert-level command of the advanced database functionalities and will be able to implement advanced administrative tasks with PostgreSQL.
Table of Contents (14 chapters)
Free Chapter
1
PostgreSQL Overview

Reassigning objects and dropping users

After assigning permissions and restricting access, it can happen that users will be dropped from the system. Unsurprisingly, the commands to do that are the DROP ROLE and DROP USER commands:

test=# h DROP ROLE 
Command: DROP ROLE
Description: remove a database role
Syntax:
DROP ROLE [ IF EXISTS ] name [, ...]

Let us give it a try:

test=# DROP ROLE joe; 
ERROR: role "joe" cannot be dropped because some objects
depend on it
DETAIL: target of policy joe_pol_3 on table t_person
target of policy joe_pol_2 on table t_person
target of policy joe_pol_1 on table t_person
privileges for table t_person
owner of table t_user
owner of sequence t_user_id_seq
owner of default privileges on new relations belonging to role joe
in schema public
owner of table t_useful

PostgreSQL will issue error messages because a user can only be removed if everything has been...