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https://issues.apache.org/jira/browse/HIVE-12369?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16112186#comment-16112186
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Matt McCline commented on HIVE-12369:
-------------------------------------
Yes, I think you continue reviewing. The path that is implemented is One Long
Key and groupByMode == HASH. There are UNDONEs for *subsequent* JIRAs that
later adds Aggregation of non-Long data types, Fixed Length Keys / Variable
Length Keys, and the other groupByModes. And later adds Grouping Sets, Empty
Aggregation (i.e. GroupBy on key that has no aggregations that does duplicate
key elimination), too.
> Native Vector GroupBy
> ---------------------
>
> Key: HIVE-12369
> URL: https://issues.apache.org/jira/browse/HIVE-12369
> Project: Hive
> Issue Type: Bug
> Components: Hive
> Reporter: Matt McCline
> Assignee: Matt McCline
> Priority: Critical
> Attachments: HIVE-12369.01.patch, HIVE-12369.02.patch,
> HIVE-12369.05.patch, HIVE-12369.06.patch
>
>
> Implement Native Vector GroupBy using fast hash table technology developed
> for Native Vector MapJoin, etc.
> Patch is currently limited to a single Long key, aggregation on Long columns,
> no more than 31 columns.
> 3 new classes introduces that stored the count in the slot table and don't
> allocate hash elements:
> {noformat}
> COUNT(column) VectorGroupByHashOneLongKeyCountColumnOperator
> COUNT(key) VectorGroupByHashOneLongKeyCountKeyOperator
> COUNT(*) VectorGroupByHashOneLongKeyCountStarOperator
> {noformat}
> And a new class that aggregates a single Long key:
> {noformat}
> VectorGroupByHashOneLongKeyOperator
> {noformat}
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