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Mastering PostgreSQL 11

You're reading from   Mastering PostgreSQL 11 Expert techniques to build scalable, reliable, and fault-tolerant database applications

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Product type Paperback
Published in Oct 2018
Publisher
ISBN-13 9781789537819
Length 446 pages
Edition 2nd Edition
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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 (15) Chapters Close

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

Optimizing storage and managing cleanup

Transactions are an integral part of the PostgreSQL system. However, transactions come with a small price tag attached. As we've already shown in this chapter, sometimes, concurrent users will be presented with different data. Not everybody will get the same data returned by a query. In addition to this, DELETE and UPDATE are not allowed to actually overwrite data since ROLLBACK would not work. If you happen to be in the middle of a large DELETE operation, you cannot be sure whether you will be able to COMMIT or not. In addition to this, data is still visible while you perform DELETE, and sometimes data is even visible once your modification has long since finished.

Consequently, this means that cleanup has to happen asynchronously. A transaction cannot clean up its own mess and COMMIT/ROLLBACK might be too early to take care of dead...

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