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From "Jinfeng Ni (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-3412) Projections are not getting push down below Window operator
Date Wed, 22 Jul 2015 20:58:04 GMT

    [ https://issues.apache.org/jira/browse/DRILL-3412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14637601#comment-14637601

Jinfeng Ni commented on DRILL-3412:

View with fewer columns will not help, I believe, since in query planning, the view will be
replaced with its view ddl statement, which will query against the base TPCDS table.

You can create another table T2 in parquet (assume you use parquet format) from the original
table T1, such that T2 only contains the columns referenced in the query. Then, do a performance
comparison, to see the impact of project pushdown on window function.

Select some_window_function from T1;

SELECT some_window_function from T2;

> Projections are not getting push down below Window operator
> -----------------------------------------------------------
>                 Key: DRILL-3412
>                 URL: https://issues.apache.org/jira/browse/DRILL-3412
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Query Planning & Optimization
>            Reporter: Aman Sinha
>            Assignee: Jinfeng Ni
>            Priority: Blocker
>             Fix For: 1.2.0
> The plan below shows that the 'star' column is being produced by the Scan and subsequent
Project.  This indicates projection pushdown is not working as desired when window function
is present.  The query produces correct results.
> {code}
> explain plan for select min(n_nationkey) over (partition by n_regionkey) from cp.`tpch/nation.parquet`
> 00-00    Screen
> 00-01      Project(EXPR$0=[$0])
> 00-02        Project(w0$o0=[$3])
> 00-03          Window(window#0=[window(partition {2} order by [] range between UNBOUNDED
> 00-04            SelectionVectorRemover
> 00-05              Sort(sort0=[$2], dir0=[ASC])
> 00-06                Project(T1¦¦*=[$0], n_nationkey=[$1], n_regionkey=[$2])
> 00-07                  Scan(groupscan=[ParquetGroupScan [entries=[ReadEntryWithPath [path=classpath:/tpch/nation.parquet]],
selectionRoot=/tpch/nation.parquet, numFiles=1, columns=[`*`]]])
> {code}

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