Gopal V created HIVE-14257:
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Summary: 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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