No, don't delete the directory. Just use a trick to optimize Firefox. I get the names and come back in a few seconds...
/Edit : you can use a command line for this, or Bleachbit. In both cases you need sqlite-tools installed.
Then, in Bleachbit, as user, with Firefox closed, tick on the different choices to clean Firefox : you may want to remove the history, or not, you will want to remove cookies... and so on, especially you will want the option "Optimize" selected.
Click on the preview button. Look at the list on the right side. If there is no file you want to keep in the given list, proceed with the button "Clean". If there is or there are files you want to keep, in the list, hit the menu "Edit > Preferences" and add the files to be kept in the white list. Then redo : preview, look, then clean.
After this, Firefox should be snappier ! If not, look at how many plugins are installed, run firefox from console and look at the messages in console, and also seek for related messages in the file $HOME/.xsession-errors.
/Edit 2 : who is interested in the command lines ? Here first, the one to list the files to be cleaned:
$ find . -name ‘*sqlite*’ -exec ls -l {} ;
then, the one to to perform the cleaning:
$ find . -name ‘*sqlite*’ -exec sqlite3 {} ‘vacuum’ ;
