presto-parser/src/main/java/io/prestosql/sql/tree/FieldReference.java/FieldReference/equals
class FieldReference:    @Override
    public boolean equals(Object o)
    {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        FieldReference that = (FieldReference) o;

        return fieldIndex == that.fieldIndex;
    }