Problem : How does hook_update_n work in Drupal.
Why we use it: We want to perform a change on a website that is already live. We cannot uninstall and re-enable the module. So we add a hook_update_n
Well Idealy its all about the naming of the hook SO it goes like this
what is 7002?
- 7 = core compatibilyty, so in this case it is compatible with Drupal 7
- 0 = you module major release version, in this case its relaease 0
- 02 = two digits for sequential counting. so this is the second change you are adding in the 0 release of your module
Where to put this:
- IN the mymodule.install file
- In your <active-profile>.install file
HOW TO RUN: basically going to update.php will do. Or else from the command line run drush updb
All the magic happens in includes/update.inc . This file collectively has a list of functions that will
- lookup the system table
- Get the latest schema_version for any installed module (Ex: 7001).
- Then call all the hook_update_n implementations in sequence 02, 03, 04 .... 99
On the database you are using you can check what the latest scema_version is by running the following query
SELECT schema_version FROM `system` WHERE name = 'mymodulename'