Nextcloud repairing missing indexes in database

When your nextcloud installation is showing an error like the following, then you could use "occ db:add-missing-indices" to repair it:

"Security & setup warnings

It's important for the security and performance of your instance that everything is configured correctly. To help you with that we are doing some automatic checks. Please see the linked documentation for more information.

There are some warnings regarding your setup.

• The database is missing some indexes. Due to the fact that adding indexes on big tables could take some time they were not added automatically. By running "occ db:add-missing-indices" those missing indexes could be added manually while the instance keeps running. Once the indexes are added queries to those tables are usually much faster.
  
  Missing index "fs_size" in table "oc_filecache".

How to fix it:

privusrA17@nextcloud042:~#
privusrA17@nextcloud042:~# cd /var/www/nextcloud; sudo -u www-data php ./occ db:add-missing-indices
Check indices of the share table.
Check indices of the filecache table.
Adding additional size index to the filecache table, this can take some time...
Filecache table updated successfully.
Check indices of the twofactor_providers table.
Check indices of the login_flow_v2 table.
Check indices of the whats_new table.
Check indices of the cards table.
Check indices of the cards_properties table.
Check indices of the calendarobjects_props table.
Check indices of the schedulingobjects table.
Check indices of the oc_properties table.
privusrA17@nextcloud042:/var/www/nextcloud#
privusrA17@nextcloud042:/var/www/nextcloud#