presto-parser/src/main/java/io/prestosql/sql/tree/ExpressionTreeRewriter.java/RewritingVisitor/visitExists
class RewritingVisitor:        @Override
        protected Expression visitExists(ExistsPredicate node, Context<C> context)
        {
            if (!context.isDefaultRewrite()) {
                Expression result = rewriter.rewriteExists(node, context.get(), ExpressionTreeRewriter.this);
                if (result != null) {
                    return result;
                }
            }

            Expression subquery = node.getSubquery();
            subquery = rewrite(subquery, context.get());

            if (subquery != node.getSubquery()) {
                return new ExistsPredicate(subquery);
            }

            return node;
        }