[jira] [Commented] (HIVE-11794) GBY vectorization appears to process COMPLETE reduce-side GBY incorrectly

["Sergey Shelukhin (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-11794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14741719#comment-14741719 ] 

Sergey Shelukhin commented on HIVE-11794:
-----------------------------------------

[~mmccline] can you take a look?

> GBY vectorization appears to process COMPLETE reduce-side GBY incorrectly
> -------------------------------------------------------------------------
>
>                 Key: HIVE-11794
>                 URL: https://issues.apache.org/jira/browse/HIVE-11794
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Sergey Shelukhin
>            Assignee: Sergey Shelukhin
>         Attachments: HIVE-11794.patch
>
>
> The code in Vectorizer is as such:
> {noformat}
>     boolean isMergePartial = (desc.getMode() != GroupByDesc.Mode.HASH);
> {noformat}
> then, if it's reduce side:
> {noformat}
>     if (isMergePartial) {
>         // Reduce Merge-Partial GROUP BY.
>         // A merge-partial GROUP BY is fed by grouping by keys from reduce-shuffle.  It is the
>         // first (or root) operator for its reduce task.
> ....
>       } else {
>         // Reduce Hash GROUP BY or global aggregation.
> ...
> {noformat}
> In fact, this logic is missing the COMPLETE mode. Both from the comment:
> {noformat}
>  COMPLETE: complete 1-phase aggregation: iterate, terminate
> ...
> HASH: For non-distinct the same as PARTIAL1 but use hash-table-based aggregation
> ...
> PARTIAL1: partial aggregation - first phase: iterate, terminatePartial
> {noformat}
> and from the explain plan like this (the query has multiple stages of aggregations over a union; the mapper does a partial hash aggregation for each side of the union, which is then followed by mergepartial, and 2nd stage as complete):
> {noformat}
> Map Operator Tree:
> ...
>         Group By Operator
>           keys: _col0 (type: int), _col1 (type: int), _col2 (type: int), _col3 (type: int), _col4 (type: int), _col5 (type: bigint), _col6 (type: bigint), _col7 (type: bigint), _col8 (type: bigint), _col9 (type: bigint), _col10 (type: bigint), _col11 (type: bigint), _col12 (type: bigint)
>           mode: hash
>           outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12
>           Reduce Output Operator
> ...
> feeding into
> Reduce Operator Tree:
>   Group By Operator
>     keys: KEY._col0 (type: int), KEY._col1 (type: int), KEY._col2 (type: int), KEY._col3 (type: int), KEY._col4 (type: int), KEY._col5 (type: bigint), KEY._col6 (type: bigint), KEY._col7 (type: bigint), KEY._col8 (type: bigint), KEY._col9 (type: bigint), KEY._col10 (type: bigint), KEY._col11 (type: bigint), KEY._col12 (type: bigint)
>     mode: mergepartial
>     outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12
>     Group By Operator
>       aggregations: sum(_col5), sum(_col6), sum(_col7), sum(_col8), sum(_col9), sum(_col10), sum(_col11), sum(_col12)
>       keys: _col0 (type: int), _col1 (type: int), _col2 (type: int), _col3 (type: int), _col4 (type: int)
>       mode: complete
>       outputColumnNames: _col0, _col1, _col2, _col3, _col4, _col5, _col6, _col7, _col8, _col9, _col10, _col11, _col12
> {noformat}
> it seems like COMPLETE is actually the global aggregation, and HASH isn't (or may not be).
> So, it seems like reduce-side COMPLETE should be handled on the else-path of the above if. For map-side, it doesn't check mode at all as far as I can see.
> Not sure if additional code changes are necessary after that, it may just work.



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