Search icon CANCEL
Arrow left icon
Explore Products
Best Sellers
New Releases
Books
Videos
Audiobooks
Learning Hub
Conferences
Free Learning
Arrow right icon
Arrow up icon
GO TO TOP
Drupal 9 Module Development

You're reading from   Drupal 9 Module Development Get up and running with building powerful Drupal modules and applications

Arrow left icon
Product type Paperback
Published in Aug 2020
Publisher Packt
ISBN-13 9781800204621
Length 626 pages
Edition 3rd Edition
Languages
Tools
Concepts
Arrow right icon
Author (1):
Arrow left icon
Daniel Sipos Daniel Sipos
Author Profile Icon Daniel Sipos
Daniel Sipos
Arrow right icon
View More author details
Toc

Table of Contents (20) Chapters Close

Preface 1. Chapter 1: Developing for Drupal 9 2. Chapter 2: Creating Your First Module FREE CHAPTER 3. Chapter 3: Logging and Mailing 4. Chapter 4: Theming 5. Chapter 5: Menus and Menu Links 6. Chapter 6: Data Modeling and Storage 7. Chapter 7: Your Own Custom Entity and Plugin Types 8. Chapter 8: The Database API 9. Chapter 9: Custom Fields 10. Chapter 10: Access Control 11. Chapter 11: Caching 12. Chapter 12: JavaScript and the Ajax API 13. Chapter 13: Internationalization and Languages 14. Chapter 14: Batches, Queues, and Cron 15. Chapter 15: Views 16. Chapter 16: Working with Files and Images 17. Chapter 17: Automated Testing 18. Chapter 18: Drupal Security 19. Other Books You May Enjoy

Query alters

Lots of things in Drupal are alterable using various hooks; queries are no different. This means that if a module writes a query such as we've seen before, other modules can alter it by implementing hook_query_alter(). So let's consider an example of how this may work.

Assume the following query, which simply returns all player records:

$result = $database->select('players', 'p')
   ->fields('p')
   ->execute();

Imagine that another module wants to alter this query and limit the results to find only the players in a specific team. There is one problem. Our query has no markers that can indicate to another module that this is the one that needs to be altered. As you can imagine, there are a bunch of queries that are run in any given request, so identifying queries becomes impossible. Enter query tags.

The previous query would not be alterable because it's not recognizable, and...

lock icon The rest of the chapter is locked
Register for a free Packt account to unlock a world of extra content!
A free Packt account unlocks extra newsletters, articles, discounted offers, and much more. Start advancing your knowledge today.
Unlock this book and the full library FREE for 7 days
Get unlimited access to 7000+ expert-authored eBooks and videos courses covering every tech area you can think of
Renews at AU $24.99/month. Cancel anytime