There should be a search button in the top bar, but according the Alia's instruction, you select everything in the ow_base_component_place_cache table, and delete.
+1 Darryl B
With 'clear' I meant, erase the value of that row or edit it and put a blank space only, not remove the row.
I just tested it on my testing website.
If you can, please make a database backup before delete more things, just in case.
Now just delete / remove all rows from 'ow_base_component_place_cache table' and reload your website.