How to clear ALL cache, including field and filter caching of nodes and fields? I'm working on a text format filter module. Now, somehow Drupal keeps the node content in some cache that is not refreshed with drush cc all, which I would have hoped to "clear all cache". This is with Cache pages for anonymous users and Cache blocks disabled.

I wrote a little script that adds " " at the end of the node body, but even running that between two drush cc alls doesn't cut it, still with cache disabled.
It's really strange. If I go to a page I haven't accessed yet, it will show me an old version what was filtered.  So I'm tempted to now also let the script access the specific node over HTTP...

Is there an easy way to really clear all cache? I guess dropping and recreating all cache_* tables could cut it but that seems a bit convoluted.
"All" cache doesn't include the filter cache and if you are working with filters then that's the one you most likely want to clear.

You can clear the filter cache by truncating the cache_filter database table.

If you have drush at your disposal, you can run drush sqlq "truncate table cache_filter;" to get the intended result. 

Please note, if you are using database prefixing you will need to add the prefix yourself, as the drush sql-query command executes the query exactly as provided.