presto-main/src/main/java/io/prestosql/sql/planner/optimizations/IndexJoinOptimizer.java/IndexSourceRewriter/visitPlan
class IndexSourceRewriter:        @Override
        public PlanNode visitPlan(PlanNode node, RewriteContext<Context> context)
        {
            // We don't know how to process this PlanNode in the context of an IndexJoin, so just give up by returning something
            return node;
        }