I have a foreman setup running 1.19 where I imported a database from a machine running foreman 1.17.
After importing the database I ran /usr/sbin/foreman-rake db:migrate to update the database to 1.19, this failed with the error "Mysql2::Error: Table 'table_preferences' already exists".

Since table_preferences was empty I dropped the table and re-ran the migration, this time without issues.
The migrate script should not fail if the table is already present.