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https://issues.apache.org/jira/browse/SPARK-32361?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17166159#comment-17166159
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ulysses you commented on SPARK-32361:
-------------------------------------
[~hyukjin.kwon] thanks for remind, added some description.
> Remove project if output is subset of child
> -------------------------------------------
>
> Key: SPARK-32361
> URL: https://issues.apache.org/jira/browse/SPARK-32361
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.1.0
> Reporter: ulysses you
> Priority: Minor
>
> We can remove some redundant project after we completed pruning column.
> e.g.,
> {code:java}
> create table t1(c1 int, c2 int) using parquet;
> explain extended
> select sum(c1) from (
> select * from t1
> );
> {code}
> Currently we get this plan.
> {code:java}
> == Physical Plan ==
> *(2) HashAggregate(keys=[], functions=[sum(cast(c1#19 as bigint))],
> output=[sum(c1)#68L])
> +- Exchange SinglePartition, true, [id=#86]
> +- *(1) HashAggregate(keys=[], functions=[partial_sum(cast(c1#19 as
> bigint))], output=[sum#70L])
> +- *(1) Project [c1#19]
> +- *(1) ColumnarToRow
> +- FileScan parquet default.t1[c1#19] Batched: true, DataFilters:
> [], Format: Parquet, Location:
> InMemoryFileIndex[hdfs:///user/hive/warehouse/t1], PartitionFilters: [],
> PushedFilters: [], ReadSchema: struct<c1:int>
> {code}
> We can remove the `Project`, like this
> {code:java}
> == Physical Plan ==
> *(2) HashAggregate(keys=[], functions=[sum(cast(c1#19 as bigint))],
> output=[sum(c1)#68L])
> +- Exchange SinglePartition, true, [id=#86]
> +- *(1) HashAggregate(keys=[], functions=[partial_sum(cast(c1#19 as
> bigint))], output=[sum#70L])
> +- *(1) ColumnarToRow
> +- FileScan parquet default.t1[c1#19] Batched: true, DataFilters:
> [], Format: Parquet, Location:
> InMemoryFileIndex[hdfs:///user/hive/warehouse/t1], PartitionFilters: [],
> PushedFilters: [], ReadSchema: struct<c1:int>
> {code}
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