presto-main/src/main/java/io/prestosql/sql/analyzer/RelationType.java/RelationType/indexOf
class RelationType:    public int indexOf(Field field)
    {
        requireNonNull(field, "field cannot be null");
        Integer index = fieldIndexes.get(field);
        checkArgument(index != null, "Field %s not found", field);
        return index;
    }