HIVE-18661, we added periodical notification based refresh in HMS cache. We shall remove periodical full refresh to simplify the code as it will no longer be used. In the mean time, we introduced mechanism to provide monotonic reads through the CachedStore.commitTransaction. This will no longer be needed after HIVE-21637. So I will remove related code as well. This will provide some performance benefits include:
1. We don't have to slow down write to catch up notification logs. Write can be done immediately and tag the cache with writeids
2. We can read from cache even if updateUsingNotificationEvents is running. Read will compare the writeids of the cache so monotonic reads will be guaranteed
I'd like to put a patch separately with HIVE-21637 so it can be tested independently. HMW will use periodical notification based refresh to update cache. And it will temporarily lift the monotonic reads guarantee until HIVE-21637 checkin.