How to make volumes permanent with Docker Compose v2

I realize other people have had similar questions but this uses v2 compose file format and I didn't find anything for that.

I want to make a very simple test app to play around with MemSQL but I can't get volumes to not get deleted after docker-compose down. If I've understood Docker Docs right, volumes shouldn't be deleted without explicitly telling it to. Everything seems to work with docker-compose up but after going down and then up again all data gets deleted from the database.

As recommended as a good practice, I'm using separate memsqldata service as a separate data layer.

Here's my docker-compose.yml:

version: '2'
services:
    app:
        build: .
        links:
            - memsql
    memsql:
        image: memsql/quickstart
        volumes_from:
            - memsqldata
        ports:
            - "3306:3306"
            - "9000:9000"
    memsqldata:
        image: memsql/quickstart
        command: /bin/true
        volumes:
            - memsqldatavolume:/data

volumes:
    memsqldatavolume:
        driver: local

This was traced back to a bad documentation from MemSQL. MemSQL data path in memsql/quickstart container is /memsql and not /var/lib/memsql like in a stand-alone installation (and in MemSQL docs), and definitely not /data like somebody told me.