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https://issues.apache.org/jira/browse/DRILL-3412?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14637569#comment-14637569
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Jinfeng Ni commented on DRILL-3412:
-----------------------------------
Although there is big impact for window functions without project pushdown, I
do not think it would be a deciding factor for window function performance,
especially if the table does not have too many columns which are not referenced
in the query.
In stead, in many cases, the performance bottleneck for window function would
be in the SORT operator, not in the SCAN operator.
> 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 PRECEDING and UNBOUNDED FOLLOWING aggs [MIN($1)])])
> 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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