Book Image

Learn PostgreSQL

By : Luca Ferrari, Enrico Pirozzi
Book Image

Learn PostgreSQL

By: Luca Ferrari, Enrico Pirozzi

Overview of this book

PostgreSQL is one of the fastest-growing open source object-relational database management systems (DBMS) in the world. As well as being easy to use, it’s scalable and highly efficient. In this book, you’ll explore PostgreSQL 12 and 13 and learn how to build database solutions using it. Complete with hands-on tutorials, this guide will teach you how to achieve the right database design required for a reliable environment. You'll learn how to install and configure a PostgreSQL server and even manage users and connections. The book then progresses to key concepts of relational databases, before taking you through the Data Definition Language (DDL) and commonly used DDL commands. To build on your skills, you’ll understand how to interact with the live cluster, create database objects, and use tools to connect to the live cluster. You’ll then get to grips with creating tables, building indexes, and designing your database schema. Later, you'll explore the Data Manipulation Language (DML) and server-side programming capabilities of PostgreSQL using PL/pgSQL, before learning how to monitor, test, and troubleshoot your database application to ensure high-performance and reliability. By the end of this book, you'll be well-versed with the Postgres database and be able to set up your own PostgreSQL instance and use it to build robust solutions.
Table of Contents (27 chapters)
Section 1: Getting Started
Section 2: Interacting with the Database
Section 3: Administering the Cluster
Section 4: Replication
Section 5: The PostegreSQL Ecosystem

Explaining MVCC

xmin is only a part of the story of managing MVCC. PostgreSQL labels every tuple in the database with four different fields named xmin (already described), xmax, cmin, and cmax. Similar to what you have learned about xmin, in order to make those fields appear in a query result, you need to explicitly reference them; for instance:

forumdb=> SELECT xmin, xmax, cmin, cmax, * FROM tags ORDER BY tag;
xmin | xmax | cmin | cmax | pk | tag | parent
4854 | 0 | 0 | 0 | 24 | c++ |
4853 | 0 | 0 | 0 | 23 | java |
4852 | 0 | 0 | 0 | 22 | perl |
4855 | 0 | 0 | 0 | 25 | unix |
(4 rows)

The meaning of xmin has been already described in a previous section: it indicates the transaction identifier of the transaction that created the tuple. The xmax field, on the other hand, indicates the xid of the transaction that invalidated the tuple, for example, because it has deleted the data. The cmin and cmax fields...