[Note that this question is better suited for the user mailing list than
dev.]
In general using ListState<T> and MapState<U, V> is recommended rather than
using ValueState<List<T>> or ValueState<Map<U, V>>.
Some of the state backends are able to optimize common access patterns for
ListState and MapState in ways that are not possible for ValueState that
happens to wrap a List or Map. In particular, the RocksDB state backend can
append to ListState without having to deserialize and reserialize the
entire list, and each element of MapState is a separate RocksDB object,
making it possible to both read and update entries in MapState without
deserializing the entire map.
David
On Fri, Jan 17, 2020 at 8:45 PM Elkhan Dadashov <elkhan.dadas...@gmail.com>
wrote:
> Hi Flinkers,
>
> Was curious about if there is any performance(memory/speed) difference
> between these two options:
>
> in window process functions, when keeping state:
>
> *1) Create a single ValueState<MyClass>, and store state in pure Java
> objects*
>
> class MyClass {
> List<OtherClass> listOtherClass;
> Map<String, SomeOtherClass> mapKeyToSomeValue;
> }
>
> public class MyProcessFunc
> extends KeyedProcessFunction<String, X, Tuple3<Long, Long, Float>> {
> ...
> ValueState<MyClass> valueState;
> ...
> }
>
> vs
>
> *2) Create ListState and MapState as 2 Flink state variables:*
>
> public class MyProcessFunc
> extends KeyedProcessFunction<String, X, Tuple3<Long, Long, Float>> {
> ...
> ListState<OtherClass> listState;
> MapState<String, SomeOtherClass> mapState;
> ...
> }
>
> Which option is a recommended way of storing the states?
>
> Thanks.
>
