presto-main/src/main/java/io/prestosql/sql/planner/ExpressionExtractor.java/ExpressionExtractor/forEachExpression
class ExpressionExtractor:    public static void forEachExpression(PlanNode plan, Consumer<Expression> expressionConsumer)
    {
        plan.accept(new Visitor(expressionConsumer, true, noLookup()), null);
    }