If the name of the migration table is not qualified, ragtime will accept any table of the same name in any schema, ignoring the schema set for the connection (see ragtime.jdbc/metadata-matches-table?).
Wouldn't it make sense to search only the schema specified for the table name as qualifier or, if the name is not qualified, the schema returned by (.getSchema conn)? I expect, that tables found in other schemas will be useless anyway as any insertions will fail.