[jira] [Commented] (HIVE-14257) CBO: Push Join through Groupby to trigger shuffle reductions

["Ashutosh Chauhan (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-14257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15419219#comment-15419219 ] 

Ashutosh Chauhan commented on HIVE-14257:
-----------------------------------------

[~gopalv] I am not sure what optimization you are suggesting here. For the query in description predicate {{ d_date_sk = 1}} should be pushed to TS and if it did then there will be no shuffle of unnecessary tuples. Is that not happening?

> CBO: Push Join through Groupby to trigger shuffle reductions
> ------------------------------------------------------------
>
>                 Key: HIVE-14257
>                 URL: https://issues.apache.org/jira/browse/HIVE-14257
>             Project: Hive
>          Issue Type: Improvement
>          Components: CBO
>            Reporter: Gopal V
>
> Similar to the optimizations in hive, already which push aggregates through a join (hive.transpose.aggr.join=true).
> {code}
> select count(v) from (select d_year, count(ss_item_sk) as v from store_sales, date_dim where ss_sold_date_sk=d_Date_sk group by d_year) w, date_dim d where d.d_year = w.d_year and d_date_sk = 1;
> {code}
> currently produces an entire aggregate of all years before discarding all of that (because obviously, there's no data for d_date_sk=1;
> This particular example is a simplified version of TPC-DS Query59's join condition, which can have a reduction in scans by applying the d_month_seq between 1185 and 1185 + 11 into the wss alias.



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