The pdf_thumbnail plugin does not exist After I tried to update the database I got the following error:


  Failed: Drupal\Component\Plugin\Exception\PluginNotFoundException:
  [error] The &quot;pdf_thumbnail&quot; plugin does not exist. in
  Drupal\Core\Plugin\DefaultPluginManager-&gt;doGetDefinition() (line 52
  of
  /home/www/sites/stdev/web/core/lib/Drupal/Component/Plugin/Discovery/DiscoveryTrait.php).


I tried to find the solution and found one of a similar issue:

drush updb fails with &quot;the &#39;media_delete_action&#39; plugin does not exist&quot; after 8.4.6 &gt; 8.5.1 update

Alas, I can't apply that solution because I don't know which module uses the pdf_thumbnail plugin. How can I find it out which module uses the plugin and solve the problem with the update?
I resolved this by first re-enabling the PDF module, and then by updating core.

In my composer setup, the PDF module was a git submodule.  However, my shared host would not work with that.  So, I removed the cached information

git rm --cached web/modules/contrib/pdf


And then I added the code in that directory to my main repo.

Next, enable the PDF module.

Finally, proceed with the update process, and run update.php or drush updb