Elasticsearch necessary in seafile 8 pro docker?

In the provided docker-compose.yml file for seafile 7 pro, seafileltd/elasticsearch-with-ik:5.6.16 is a required docker image. There is no provided docker-compose for seafile 8 pro, despite seafile 8 pro being available in the docker repo. Now for the question: is seafileltd/elasticsearch-with-ik:5.6.16 still necessary? I have seafile 8 pro set up with a docker-compose file, without specifying seafileltd/elasticsearch-with-ik:5.6.16 and it works normally. What am I missing by omitting it? And if it is necessary: version 5.6.16 provided by seafileltd is not the most current version, as the official repo is on version 7.12.1.

Isn’t it used for file searching (search index)? Its in the docs manual.