The engine takes 5 - 7 parameters: the server address (host and port); the name of the database; the name of the table; the user's name; the user's password. Example:
If `replace_query` is specified to 1, then `INSERT INTO` query to this table would be transformed to `REPLACE INTO`.
If `on_duplicate_clause` is specified, eg `update impression = values(impression) + impression`, it would add `on_duplicate_clause` to the end of the MySQL insert sql.
If both `replace_query` and `on_duplicate_clause` are specified, only the `on_duplicate_clause` will work.