presto-main/src/main/java/io/prestosql/sql/planner/optimizations/PredicatePushDown.java/Rewriter/joinEqualityExpression
class Rewriter:        private boolean joinEqualityExpression(Expression expression, Collection<Symbol> leftSymbols, Collection<Symbol> rightSymbols)
        {
            // At this point in time, our join predicates need to be deterministic
            if (isDeterministic(expression, metadata) && expression instanceof ComparisonExpression) {
                ComparisonExpression comparison = (ComparisonExpression) expression;
                if (comparison.getOperator() == ComparisonExpression.Operator.EQUAL) {
                    Set<Symbol> symbols1 = SymbolsExtractor.extractUnique(comparison.getLeft());
                    Set<Symbol> symbols2 = SymbolsExtractor.extractUnique(comparison.getRight());
                    if (symbols1.isEmpty() || symbols2.isEmpty()) {
                        return false;
                    }
                    return (leftSymbols.containsAll(symbols1) && rightSymbols.containsAll(symbols2)) ||
                            (rightSymbols.containsAll(symbols1) && leftSymbols.containsAll(symbols2));
                }
            }
            return false;
        }