Hi David, Thanks for you reply. Yes, for keyed state, every state is referenced by a particular key, but I would guess it is a flink sdk issue, I mean, the keyed state maybe saved as (key, keyed state), as for my situation, it is (key, mapstate(UK,UV)), I think the key of this pair is not easy to get by user, when I do mapstate.keyset I want to get the UK set, not the key set. According to my job, the (key, mapstate(UK,UV)) can be get successfully when job is running, but when job restarts from a checkpoint, the restored mapstate, the pair seemed be changed to (key, UV), the UK just gone, I can not find back the UK. I think the key of (key, mapstate(UK,UV)) will be implictly added when write or read from the state by flink. So, I am still not clear why I get the key but not the UK.
Yours Josh David Morávek <[email protected]> 于2021年12月29日周三 17:32写道： > Hi Josh, > > it's important bit to understand is that the MapState (or any other keyed > state) is scoped per *key* [1]. You can think about it in a way, that for > each key you have a separate "map" that backs it. This is the important > concept behind distributed stream processing, that allows you to > parallelize the computation and still make sure, that all data for the same > key end up in the same partition. > > Does this answer your question? > > [1] > https://nightlies.apache.org/flink/flink-docs-release-1.14/docs/concepts/stateful-stream-processing/#keyed-state > > Best, > D. >
