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Posted to issues@spark.apache.org by "Apache Spark (JIRA)" <ji...@apache.org> on 2017/07/24 10:37:00 UTC
[jira] [Commented] (SPARK-21520) Hivetable scan for all the columns
the SQL statement contains the 'rand'
[ https://issues.apache.org/jira/browse/SPARK-21520?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16098190#comment-16098190 ]
Apache Spark commented on SPARK-21520:
--------------------------------------
User 'heary-cao' has created a pull request for this issue:
https://github.com/apache/spark/pull/18725
> Hivetable scan for all the columns the SQL statement contains the 'rand'
> ------------------------------------------------------------------------
>
> Key: SPARK-21520
> URL: https://issues.apache.org/jira/browse/SPARK-21520
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.3.0
> Reporter: caoxuewen
>
> Currently, when the rand function is present in the SQL statement, hivetable searches all columns in the table.
> e.g:
> select k,k,sum(id) from (select d004 as id, floor(rand() * 10000) as k, ceil(c010) as cceila from XXX_table) a
> group by k,k;
> generate WholeStageCodegen subtrees:
> == Subtree 1 / 2 ==
> *HashAggregate(keys=[k#403L], functions=[partial_sum(cast(id#402 as bigint))], output=[k#403L, sum#800L])
> +- Project [d004#607 AS id#402, FLOOR((rand(8828525941469309371) * 10000.0)) AS k#403L]
> +- HiveTableScan [c030#606L, d004#607, d005#608, d025#609, c002#610, d023#611, d024#612, c005#613L, c008#614, c009#615, c010#616, d021#617, d022#618, c017#619, c018#620, c019#621, c020#622, c021#623, c022#624, c023#625, c024#626, c025#627, c026#628, c027#629, ... 169 more fields], MetastoreRelation XXX_database, XXX_table
> == Subtree 2 / 2 ==
> *HashAggregate(keys=[k#403L], functions=[sum(cast(id#402 as bigint))], output=[k#403L, k#403L, sum(id)#797L])
> +- Exchange hashpartitioning(k#403L, 200)
> +- *HashAggregate(keys=[k#403L], functions=[partial_sum(cast(id#402 as bigint))], output=[k#403L, sum#800L])
> +- Project [d004#607 AS id#402, FLOOR((rand(8828525941469309371) * 10000.0)) AS k#403L]
> +- HiveTableScan [c030#606L, d004#607, d005#608, d025#609, c002#610, d023#611, d024#612, c005#613L, c008#614, c009#615, c010#616, d021#617, d022#618, c017#619, c018#620, c019#621, c020#622, c021#623, c022#624, c023#625, c024#626, c025#627, c026#628, c027#629, ... 169 more fields], MetastoreRelation XXX_database, XXX_table
>
> All columns will be searched in HiveTableScans , Consequently, All column data is read to a ORC table.
> e.g:
> INFO ReaderImpl: Reading ORC rows from hdfs://opena:8020/.../XXX_table/.../p_date=2017-05-25/p_hour=10/part-00009 with {include: [true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true, true], offset: 0, length: 9223372036854775807}
> so, The execution of the SQL statement will become very slow.
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