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https://issues.apache.org/jira/browse/FLINK-8639?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16369216#comment-16369216
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ASF GitHub Bot commented on FLINK-8639:
---------------------------------------

Github user StefanRRichter commented on a diff in the pull request:

    https://github.com/apache/flink/pull/5465#discussion_r169100675
  
    --- Diff: 
flink-contrib/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBMapState.java
 ---
    @@ -400,7 +410,7 @@ public UV setValue(UV value) {
        /** An auxiliary utility to scan all entries under the given key. */
        private abstract class RocksDBMapIterator<T> implements Iterator<T> {
     
    -           static final int CACHE_SIZE_BASE = 1;
    +           static final int CACHE_SIZE_BASE = 32;
    --- End diff --
    
    Why is 32 the magic value and not 16 or 64? Just asking :)


> Fix always need to seek multiple times when iterator RocksDBMapState
> --------------------------------------------------------------------
>
>                 Key: FLINK-8639
>                 URL: https://issues.apache.org/jira/browse/FLINK-8639
>             Project: Flink
>          Issue Type: Improvement
>          Components: State Backends, Checkpointing
>    Affects Versions: 1.4.0
>            Reporter: Sihua Zhou
>            Assignee: Sihua Zhou
>            Priority: Critical
>             Fix For: 1.5.0
>
>
> Currently, almost every time we want to iterator a RocksDBMapState we need to 
> do seek at least 2 times (Seek is a poor performance action for rocksdb cause 
> it can't use the bloomfilter). This is because `RocksDBMapIterator` use a 
> `cacheEntries` to cache the seek values every time and the `cacheEntries`'s 
> init size is 1.



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