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Posted to issues@spark.apache.org by "Apache Spark (JIRA)" <ji...@apache.org> on 2019/03/13 18:36:00 UTC
[jira] [Commented] (SPARK-27123) Improve CollapseProject to handle
projects cross limit/repartition/sample
[ https://issues.apache.org/jira/browse/SPARK-27123?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16791991#comment-16791991 ]
Apache Spark commented on SPARK-27123:
--------------------------------------
User 'dongjoon-hyun' has created a pull request for this issue:
https://github.com/apache/spark/pull/24078
> Improve CollapseProject to handle projects cross limit/repartition/sample
> -------------------------------------------------------------------------
>
> Key: SPARK-27123
> URL: https://issues.apache.org/jira/browse/SPARK-27123
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: Dongjoon Hyun
> Assignee: Dongjoon Hyun
> Priority: Major
> Fix For: 3.0.0
>
>
> `CollapseProject` optimizer simplifies the plan by merging the adjacent projects and performing alias substitution.
> {code:java}
> scala> sql("SELECT b c FROM (SELECT a b FROM t)").explain
> == Physical Plan ==
> *(1) Project [a#5 AS c#1]
> +- Scan hive default.t [a#5], HiveTableRelation `default`.`t`, org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, [a#5]
> {code}
> We can do that more complex cases like the following.
> *BEFORE*
> {code:java}
> scala> sql("SELECT b c FROM (SELECT /*+ REPARTITION(1) */ a b FROM t)").explain
> == Physical Plan ==
> *(2) Project [b#0 AS c#1]
> +- Exchange RoundRobinPartitioning(1)
> +- *(1) Project [a#5 AS b#0]
> +- Scan hive default.t [a#5], HiveTableRelation `default`.`t`, org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, [a#5]
> {code}
> *AFTER*
> {code:java}
> scala> sql("SELECT b c FROM (SELECT /*+ REPARTITION(1) */ a b FROM t)").explain
> == Physical Plan ==
> Exchange RoundRobinPartitioning(1)
> +- *(1) Project [a#11 AS c#7]
> +- Scan hive default.t [a#11], HiveTableRelation `default`.`t`, org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, [a#11]
> {code}
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