[jira] [Commented] (SPARK-9066) Improve cartesian performance

["Apache Spark (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-9066?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14627770#comment-14627770 ] 

Apache Spark commented on SPARK-9066:
-------------------------------------

User 'Sephiroth-Lin' has created a pull request for this issue:
https://github.com/apache/spark/pull/7417

> 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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