Weizhong created SPARK-9066:
-------------------------------
Summary: Improve cartesian performance
Key: SPARK-9066
URL: https://issues.apache.org/jira/browse/SPARK-9066
Project: Spark
Issue Type: Improvement
Components: SQL
Reporter: Weizhong
Priority: Minor
Currently, for CartesianProduct, if right plan partition number are small than
left partition number, then then performance is bad as need do many times scan
for right plan.
For example:
{noformat}
with single_value as (
select max(1) tpcds_val from date_dim
)
select sum(ss_quantity * ss_sales_price) ssales, tpcds_val
from store_sales, single_value
group by tpcds_val
{noformat}
above SQL clause, right plan only have 1 partition, left plan have 1823
partiton(in our test), then for each left plan partition we need scan data from
hdfs for right plan.
That is, for left plan we need scan _left_plan_partition_num_ times, for right
plan we need scan _left_plan_partition_num * right_plan_partition_num_ times,
total is _left_plan_partition_num * left_plan_partition_num *
right_plan_partition_num_ times
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