[GitHub] [flink] JingsongLi commented on a change in pull request #10756: [FLINK-15465][FLINK-11964][table-runtime-blink] Fix hash table bugs

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JingsongLi commented on a change in pull request #10756: [FLINK-15465][FLINK-11964][table-runtime-blink] Fix hash table bugs
URL: https://github.com/apache/flink/pull/10756#discussion_r363143078
 
 

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 File path: flink-table/flink-table-runtime-blink/src/main/java/org/apache/flink/table/runtime/hashtable/BaseHybridHashTable.java
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 @@ -516,4 +511,10 @@ public static int hash(int hashCode, int level) {
 		return code >= 0 ? code : -(code + 1);
 	}
 
+	/**
+	 * Partition level hash again, for avoid two layer hash conflict.
+	 */
+	static int partitionLevelHash(int hash) {
+		return hash ^ (hash >>> 16);
+	}
 
 Review comment:
   Thanks for involving this.
   > with most high bits equal to 0
   
   Good point, but it should not. 
   - In `BinaryHashTable`: HashCode is from murmurhash, it is good.
   - In `LongHybridHashTable`: HashCode is from `hashLong`, it is good too.
   
   `hash ^ (hash >>> 16)` is just from `HashMap.hash`, I think it is OK.

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