Davies Liu created SPARK-13347:
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Summary: Reuse the shuffle for duplicated exchange
Key: SPARK-13347
URL: https://issues.apache.org/jira/browse/SPARK-13347
Project: Spark
Issue Type: Improvement
Components: SQL
Reporter: Davies Liu
In TPCDS query 47, the same exchange is used three times, we should re-use the
ShuffleRowRDD to skip the duplicated stages.
{code}
with v1 as(
select i_category, i_brand,
s_store_name, s_company_name,
d_year, d_moy,
sum(ss_sales_price) sum_sales,
avg(sum(ss_sales_price)) over
(partition by i_category, i_brand,
s_store_name, s_company_name, d_year)
avg_monthly_sales,
rank() over
(partition by i_category, i_brand,
s_store_name, s_company_name
order by d_year, d_moy) rn
from item, store_sales, date_dim, store
where ss_item_sk = i_item_sk and
ss_sold_date_sk = d_date_sk and
ss_store_sk = s_store_sk and
(
d_year = 1999 or
( d_year = 1999-1 and d_moy =12) or
( d_year = 1999+1 and d_moy =1)
)
group by i_category, i_brand,
s_store_name, s_company_name,
d_year, d_moy),
v2 as(
select v1.i_category, v1.i_brand, v1.s_store_name, v1.s_company_name,
v1.d_year,
v1.d_moy, v1.avg_monthly_sales ,v1.sum_sales,
v1_lag.sum_sales psum,
v1_lead.sum_sales nsum
from v1, v1 v1_lag, v1 v1_lead
where v1.i_category = v1_lag.i_category and
v1.i_category = v1_lead.i_category and
v1.i_brand = v1_lag.i_brand and
v1.i_brand = v1_lead.i_brand and
v1.s_store_name = v1_lag.s_store_name and
v1.s_store_name = v1_lead.s_store_name and
v1.s_company_name = v1_lag.s_company_name and
v1.s_company_name = v1_lead.s_company_name and
v1.rn = v1_lag.rn + 1 and
v1.rn = v1_lead.rn - 1)
select * from v2
where d_year = 1999 and
avg_monthly_sales > 0 and
case when avg_monthly_sales > 0 then abs(sum_sales - avg_monthly_sales)
/ avg_monthly_sales else null end > 0.1
order by sum_sales - avg_monthly_sales, 3
limit 100
{code}
Since the SparkPlan is just a tree (not DAG), we can only do this in
SparkPlan.execute() or final rule.
And we should also have a way to compare two SparkPlan whether they have same
result or not (they may have different exprId, we should compare them after
bind).
An quick experiment showed that we could have 2X improvement on this query.
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