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https://issues.apache.org/jira/browse/FLINK-26738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17511363#comment-17511363
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Jianhui Dong commented on FLINK-26738:
--------------------------------------

And I think this is an issue worth discussing, from my personal point of view, 
if the default value is valid for TTL state, there's no difference between 
having the user set a default value to the state descriptor and replacing the 
expired state with a default value in the code manually. Even if a user sets 
the default value, they can also replace it with a new value, it's no conflict 
and would make the concept of default value clearer.
And one more question, why we add @Deprecated annotation to the ValueDescriptor 
constructor, would we remove the default value in class StateDescriptor in the 
future?

> Default value of StateDescriptor is valid when enable state ttl config
> ----------------------------------------------------------------------
>
>                 Key: FLINK-26738
>                 URL: https://issues.apache.org/jira/browse/FLINK-26738
>             Project: Flink
>          Issue Type: Bug
>          Components: API / Core
>    Affects Versions: 1.15.0
>            Reporter: Jianhui Dong
>            Priority: Critical
>
> Suppose we declare a ValueState like following:
> {code:java}
> ValueStateDescriptor<Tuple2<Long, Long>> descriptor =
>                 new ValueStateDescriptor<>(
>                         "average", // the state name
>                         TypeInformation.of(new TypeHint<Tuple2<Long, Long>>() 
> {}),  
>                         Tuple2.of(0L, 0L)); 
> {code}
> and then we add state ttl config to the state:
> {code:java}
> descriptor.enableTimeToLive(StateTtlConfigUtil.createTtlConfig(60000));
> {code}
> the default value Tuple2.of(0L, 0L) will be invalid and may cause NPE.
> I don't know if this is a bug cause I see @Deprecated in the comment of the 
> ValueStateDescriptor constructor with argument defaultValue:
> {code:java}
> Use {@link #ValueStateDescriptor(String, TypeSerializer)} instead and manually
>      *     manage the default value by checking whether the contents of the 
> state is {@code null}.
> {code}
> and if we decide not to use the defaultValue field in the class 
> StateDescriptor, should we add @Deprecated annotation to the field 
> defaultValue?



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