[jira] Created: (HIVE-1472) reduce the usage of HashMap and List.iterator.

["He Yongqiang (JIRA)" <ji...@apache.org>]

reduce the usage of HashMap and List.iterator. 
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                 Key: HIVE-1472
                 URL: https://issues.apache.org/jira/browse/HIVE-1472
             Project: Hadoop Hive
          Issue Type: Improvement
            Reporter: He Yongqiang
            Priority: Minor


 HashMap is used in a lot of places in Hive. Most times we can just replace it with native array. List.iterator() give a lot of pressure to Java GC, we should avoid it.
Another thing we can also try here is to replace GroupByOperator's HashMap look up by not using the ObjectInspectorUtils.compare(). Instead, We can try here is to first serialize the keys and use the serialized bytes to do the comparison.

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