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https://issues.apache.org/jira/browse/FLINK-17178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17084906#comment-17084906
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Kurt Young commented on FLINK-17178:
------------------------------------

Firstly, I'm not sure we should introduce CachedLookupFunction since it will 
effect query semantics and we seems doesn't have a clear explanation about 
that. And provides cache all strategy by extending from such 
CachedLookupFunction will certainly not a good idea. 

But cache all is a special case which could be handled by "scan the data into 
state and then do the join", it equivalents to broadcast hash join. 

If we want to support that, I will recommend to do it in another way. 

>  Provide "ALL" cache strategy in LookupFunction
> -----------------------------------------------
>
>                 Key: FLINK-17178
>                 URL: https://issues.apache.org/jira/browse/FLINK-17178
>             Project: Flink
>          Issue Type: New Feature
>          Components: Connectors / Common
>            Reporter: Lijie Wang
>            Priority: Major
>
> We provide "ALL" cache strategy mentioned in FLINK-13252, motivation as 
> follow:
> Maintain the entire dimension table in memory to improve performance. There 
> is no IO overhead when we lookup the cached table. Reload dimension table 
> periodically for update, and we can reload asynchronously with little IO 
> delay.



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