[
https://issues.apache.org/jira/browse/SPARK-22204?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Hyukjin Kwon resolved SPARK-22204.
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Resolution: Incomplete
> Explain output for SQL with commands shows no optimization
> ----------------------------------------------------------
>
> Key: SPARK-22204
> URL: https://issues.apache.org/jira/browse/SPARK-22204
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.3.0
> Reporter: Andrew Ash
> Priority: Major
> Labels: bulk-closed
>
> When displaying the explain output for a basic SELECT query, the query plan
> changes as expected from analyzed -> optimized stages. But when putting that
> same query into a command, for example {{CREATE TABLE}} it appears that the
> optimization doesn't take place.
> In Spark shell:
> Explain output for a {{SELECT}} statement shows optimization:
> {noformat}
> scala> spark.sql("SELECT a FROM (SELECT a FROM (SELECT a FROM (SELECT 1 AS a)
> AS b) AS c) AS d").explain(true)
> == Parsed Logical Plan ==
> 'Project ['a]
> +- 'SubqueryAlias d
> +- 'Project ['a]
> +- 'SubqueryAlias c
> +- 'Project ['a]
> +- SubqueryAlias b
> +- Project [1 AS a#29]
> +- OneRowRelation
> == Analyzed Logical Plan ==
> a: int
> Project [a#29]
> +- SubqueryAlias d
> +- Project [a#29]
> +- SubqueryAlias c
> +- Project [a#29]
> +- SubqueryAlias b
> +- Project [1 AS a#29]
> +- OneRowRelation
> == Optimized Logical Plan ==
> Project [1 AS a#29]
> +- OneRowRelation
> == Physical Plan ==
> *Project [1 AS a#29]
> +- Scan OneRowRelation[]
> scala>
> {noformat}
> But the same command run inside {{CREATE TABLE}} does not:
> {noformat}
> scala> spark.sql("CREATE TABLE IF NOT EXISTS tmptable AS SELECT a FROM
> (SELECT a FROM (SELECT a FROM (SELECT 1 AS a) AS b) AS c) AS d").explain(true)
> == Parsed Logical Plan ==
> 'CreateTable `tmptable`, org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe,
> Ignore
> +- 'Project ['a]
> +- 'SubqueryAlias d
> +- 'Project ['a]
> +- 'SubqueryAlias c
> +- 'Project ['a]
> +- SubqueryAlias b
> +- Project [1 AS a#33]
> +- OneRowRelation
> == Analyzed Logical Plan ==
> CreateHiveTableAsSelectCommand [Database:default}, TableName: tmptable,
> InsertIntoHiveTable]
> +- Project [a#33]
> +- SubqueryAlias d
> +- Project [a#33]
> +- SubqueryAlias c
> +- Project [a#33]
> +- SubqueryAlias b
> +- Project [1 AS a#33]
> +- OneRowRelation
> == Optimized Logical Plan ==
> CreateHiveTableAsSelectCommand [Database:default}, TableName: tmptable,
> InsertIntoHiveTable]
> +- Project [a#33]
> +- SubqueryAlias d
> +- Project [a#33]
> +- SubqueryAlias c
> +- Project [a#33]
> +- SubqueryAlias b
> +- Project [1 AS a#33]
> +- OneRowRelation
> == Physical Plan ==
> CreateHiveTableAsSelectCommand CreateHiveTableAsSelectCommand
> [Database:default}, TableName: tmptable, InsertIntoHiveTable]
> +- Project [a#33]
> +- SubqueryAlias d
> +- Project [a#33]
> +- SubqueryAlias c
> +- Project [a#33]
> +- SubqueryAlias b
> +- Project [1 AS a#33]
> +- OneRowRelation
> scala>
> {noformat}
> Note that there is no change between the analyzed and optimized plans when
> run in a command.
> This is misleading my users, as they think that there is no optimization
> happening in the query!
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