presto-main/src/main/java/io/prestosql/cost/ComparisonStatsCalculator.java/ComparisonStatsCalculator/estimateExpressionToExpressionComparison
class ComparisonStatsCalculator:    public static PlanNodeStatsEstimate estimateExpressionToExpressionComparison(
            PlanNodeStatsEstimate inputStatistics,
            SymbolStatsEstimate leftExpressionStatistics,
            Optional<Symbol> leftExpressionSymbol,
            SymbolStatsEstimate rightExpressionStatistics,
            Optional<Symbol> rightExpressionSymbol,
            ComparisonExpression.Operator operator)
    {
        switch (operator) {
            case EQUAL:
                return estimateExpressionEqualToExpression(inputStatistics, leftExpressionStatistics, leftExpressionSymbol, rightExpressionStatistics, rightExpressionSymbol);
            case NOT_EQUAL:
                return estimateExpressionNotEqualToExpression(inputStatistics, leftExpressionStatistics, leftExpressionSymbol, rightExpressionStatistics, rightExpressionSymbol);
            case LESS_THAN:
            case LESS_THAN_OR_EQUAL:
            case GREATER_THAN:
            case GREATER_THAN_OR_EQUAL:
            case IS_DISTINCT_FROM:
                return PlanNodeStatsEstimate.unknown();
            default:
                throw new IllegalArgumentException("Unexpected comparison operator: " + operator);
        }
    }