@Override
    public String toString() {
        SQLSerializer serializer = createSerializer();
        serializer.serializeMerge(metadata, entity, keys, columns, values, subQuery);
        return serializer.toString();
    }
Set the keys to be used in the MERGE clause

@param paths keys
@return the current object
querydsl-sql/src/main/java/com/querydsl/sql/dml/SQLMergeClause.java