@User this has to do with an incompatbility between the broker and server for specific types of queries. Assuming you upgrade in the order controller, broker, server, then before upgrading server (but after upgrading broker) you will get errors if these type of queries are issued to the broker. The types of queries are selection with order by i believe, but @User can provide specific examples.
06/12/2020, 6:16 PM
Thanks. The parts that I do not get is why a direct 0.1->0.3 upgrade is not possible. does it mean the code of retaining compatibility is only available in 0.2 but not later version?
Otherwise 0.1.0 would have been incompat with all releases moving forward
Please discuss with @Jackie as to specific queries that affect the situation., If you are not using those queries, you should be fine upgrading directly. Or, if you are wilkling to take a short downtime, you should be able to upgrade directly. The situation happens ONLY when brokers are at 0.3.0 but servers are in 0.1.0 (or vice versa). If you are abke to take some query failures during the uypgrade, that is also fine.