Special files under dovecot mail box

Hello, even if all the mails(messages) are deleted from my mail box (such as the sent box), the capacity of the following special files will not change, that is, these files will only increase and easily occupy the disk. Is there any other way besides using doveadm index manually? In addition, will these files be affected if they are deleted?

-rw-------. 1 vmail vmail 3912 Dec 1 13:52 dovecot.index -rw-------. 1 vmail vmail 127008 Dec 17 17:21 dovecot.index.cache -rw-------. 1 vmail vmail 18800 Dec 17 17:21 dovecot.index.log -rw-------. 1 vmail vmail 1567 Jun 20 2019 dovecot.index.thread

Dovecot version is 2.2.36.