Which tables should be emptied when clearing database-stored cache manually?

Question

Prior to D8 to clear cache manually one could truncate all tables beginning with cache_.

In Drupal 8 there are still tables starting with cache_, but there's also a cachetags table.

Is the advice in D8 still to truncate cache_* if you need to clear cache manually? Is it safe/required/recommended to truncate the cachetags table along with the cache_* tables?

I'm aware there may be contrib modules doing things differently, I'm mostly interested in what core does, and what's considered "best practice" for Drupal 8 in general.

Answer 1

In drupal 8 if you are looking for the safe tables that needs to be cleared manually then clear the tables starting with cache_ and also truncate the cachetags table too.

If you are using drush then use this command for clear cache-

drush cache-rebuild

Answer 2

According to this article cachetags are set when cache objects are being stored, so it should be safe to truncate this table also. Cachetags identify cache objects and you can get all related objects at once.

Answer 3

You could do this for a one-liner:

drush sqlq "TRUNCATE cache_default;TRUNCATE cache_bootstrap;TRUNCATE cache_container;TRUNCATE cache_discovery;TRUNCATE cache_data;" -l <uri> --no-interaction

Add as many with cache_ prefix as you would like.

Answer 4

This is very handy. Replace dbname as needed:

DB_NAME="dbname"

mysql -uroot -proot --execute="SELECT concat('TRUNCATE TABLE ', TABLE_NAME, ';') FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = '${DB_NAME}' AND TABLE_NAME LIKE '%cache%'" | sed 1d | mysql -uroot -proot ${DB_NAME};