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https://issues.apache.org/jira/browse/SPARK-9066?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-9066:
-----------------------------------
Assignee: (was: Apache Spark)
> 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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