Execute the following commands, before pulling:
docker-compose up -d
docker-compose exec postgres pg_dump danbooru2 -U danbooru > backup.sql
docker-compose down
docker volume rm e621ng_db_data
Execute the following commands, after pulling:
docker-compose up -d
docker-compose exec -T postgres psql -d e621_development -U e621 < backup.sql
This also changes the name of the database and role.
Now seems like a nice opportunity to do so.