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https://issues.apache.org/jira/browse/HIVE-1738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12923759#action_12923759
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Zheng Shao commented on HIVE-1738:
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+1. This is smart!
> public boolean areEqual(ArrayList<Object> ol0, ArrayList<Object> ol1) ...
Why do we need to care about the case that the 2 array lists are different in
size / shorter than numFields?
> for (int i = 0; i < numFields; i++) {
We might want to try comparing the last field first. The reason is that in
sort-based aggregation, the last key is more likely to be different than the
first key. Not sure the effect is big enough to be noticeable though.
> Optimize Key Comparison in GroupByOperator
> ------------------------------------------
>
> Key: HIVE-1738
> URL: https://issues.apache.org/jira/browse/HIVE-1738
> Project: Hive
> Issue Type: Improvement
> Reporter: Siying Dong
> Assignee: Siying Dong
> Fix For: 0.7.0
>
> Attachments: HIVE.1738.1.patch, HIVE.1738.2.patch, HIVE.1738.3.patch
>
>
> GroupByOperator uses ObjectInspectorUtils.compare() to compare keys, which is
> written for generalized object comparisons, which is not optimized for
> group-by operator. By optimizing this logic, we expect to see obvious
> improvements in GroupByOperator.
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