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Mastering PostgreSQL 15

You're reading from   Mastering PostgreSQL 15 Advanced techniques to build and manage scalable, reliable, and fault-tolerant database applications

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Product type Paperback
Published in Jan 2023
Publisher Packt
ISBN-13 9781803248349
Length 522 pages
Edition 5th Edition
Languages
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Author (1):
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Hans-Jürgen Schönig Hans-Jürgen Schönig
Author Profile Icon Hans-Jürgen Schönig
Hans-Jürgen Schönig
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Table of Contents (16) Chapters Close

Preface 1. Chapter 1: PostgreSQL 15 Overview 2. Chapter 2: Understanding Transactions and Locking FREE CHAPTER 3. Chapter 3: Making Use of Indexes 4. Chapter 4: Handling Advanced SQL 5. Chapter 5: Log Files and System Statistics 6. Chapter 6: Optimizing Queries for Good Performance 7. Chapter 7: Writing Stored Procedures 8. Chapter 8: Managing PostgreSQL Security 9. Chapter 9: Handling Backup and Recovery 10. Chapter 10: Making Sense of Backups and Replication 11. Chapter 11: Deciding on Useful Extensions 12. Chapter 12: Troubleshooting PostgreSQL 13. Chapter 13: Migrating to PostgreSQL 14. Index 15. Other Books You May Enjoy

Making use of replication slots

After that introduction to synchronous replication and dynamically adjustable durability, I want to focus on a feature called replication slots.

What is the purpose of a replication slot? Let’s consider the following example – there is a master and a slave. On the master, a large transaction is executed, and the network connection is not fast enough to ship all data in time. At some point, the master removes its transaction log (checkpoint). If the slave is too far behind, a resync is needed. As we have already seen, the wal_keep_segments setting can be used to reduce the risk of failing replication. The question is this – what is the best value for the wal_keep_segments setting? Sure, more is better, but how much is best?

Replication slots will solve this problem for us – if we are using a replication slot, a master can only recycle the transaction log once it has been consumed by all replicas. The advantage here is...

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