Zoltan Haindrich created HIVE-20850:
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Summary: Add rule to extract case conditional from projections
Key: HIVE-20850
URL: https://issues.apache.org/jira/browse/HIVE-20850
Project: Hive
Issue Type: Improvement
Reporter: Zoltan Haindrich
Assignee: Zoltan Haindrich
noticed by [~gopalv]: If there is a project which could be only evaluated after
the join; but the condition references only a single column from a small
dimension table; hive will end up evaluating the same thing over and over
again...
{code}
explain
select s_store_name, s_store_id,
sum(case when (d_day_name='Sunday') then ss_sales_price else null end)
sun_sales,
sum(case when (d_day_name='Monday') then ss_sales_price else null end)
mon_sales,
sum(case when (d_day_name='Tuesday') then ss_sales_price else null
end) tue_sales,
sum(case when (d_day_name='Wednesday') then ss_sales_price else null
end) wed_sales,
sum(case when (d_day_name='Thursday') then ss_sales_price else null
end) thu_sales,
sum(case when (d_day_name='Friday') then ss_sales_price else null end)
fri_sales,
sum(case when (d_day_name='Saturday') then ss_sales_price else null
end) sat_sales
from date_dim, store_sales, store
where d_date_sk = ss_sold_date_sk and
s_store_sk = ss_store_sk and
s_gmt_offset = -6 and
d_year = 1998
group by s_store_name, s_store_id
order by s_store_name,
s_store_id,sun_sales,mon_sales,tue_sales,wed_sales,thu_sales,fri_sales,sat_sales
limit 100;
{code}
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