presto-parser/src/main/java/io/prestosql/sql/tree/ComparisonExpression.java/Operator/flip
class Operator:        public Operator flip()
        {
            switch (this) {
                case EQUAL:
                    return EQUAL;
                case NOT_EQUAL:
                    return NOT_EQUAL;
                case LESS_THAN:
                    return GREATER_THAN;
                case LESS_THAN_OR_EQUAL:
                    return GREATER_THAN_OR_EQUAL;
                case GREATER_THAN:
                    return LESS_THAN;
                case GREATER_THAN_OR_EQUAL:
                    return LESS_THAN_OR_EQUAL;
                case IS_DISTINCT_FROM:
                    return IS_DISTINCT_FROM;
                default:
                    throw new IllegalArgumentException("Unsupported comparison: " + this);
            }
        }