[jira] [Assigned] (SPARK-14032) Eliminate Unnecessary Distinct/Aggregate

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

     [ https://issues.apache.org/jira/browse/SPARK-14032?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Apache Spark reassigned SPARK-14032:
------------------------------------

    Assignee: Apache Spark

> Eliminate Unnecessary Distinct/Aggregate
> ----------------------------------------
>
>                 Key: SPARK-14032
>                 URL: https://issues.apache.org/jira/browse/SPARK-14032
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 2.0.0
>            Reporter: Xiao Li
>            Assignee: Apache Spark
>
> Distinct is an expensive operation. If possible, we should avoid it. When the child operators can guarantee the distinct, we can remove it.
> For example, in the following TPC-DS query 38, the child is distinct, and thus, we can remove the top Distinct after converting Intersect to Left-semi + Distinct.
> {code}
> select count(*) from (
>     select distinct c_last_name, c_first_name, d_date
>     from store_sales, date_dim, customer
>           where store_sales.ss_sold_date_sk = date_dim.d_date_sk
>       and store_sales.ss_customer_sk = customer.c_customer_sk
>       and d_month_seq between [DMS] and [DMS] + 11
>   intersect
>     select distinct c_last_name, c_first_name, d_date
>     from catalog_sales, date_dim, customer
>           where catalog_sales.cs_sold_date_sk = date_dim.d_date_sk
>       and catalog_sales.cs_bill_customer_sk = customer.c_customer_sk
>       and d_month_seq between [DMS] and [DMS] + 11
>   intersect
>     select distinct c_last_name, c_first_name, d_date
>     from web_sales, date_dim, customer
>           where web_sales.ws_sold_date_sk = date_dim.d_date_sk
>       and web_sales.ws_bill_customer_sk = customer.c_customer_sk
>       and d_month_seq between [DMS] and [DMS] + 11
> ) hot_cyst
> {code}



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