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Posted to issues@spark.apache.org by "Dilip Biswal (JIRA)" <ji...@apache.org> on 2018/10/27 18:09:00 UTC
[jira] [Commented] (SPARK-25833) Views without column names created
by Hive are not readable by Spark
[ https://issues.apache.org/jira/browse/SPARK-25833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16666178#comment-16666178 ]
Dilip Biswal commented on SPARK-25833:
--------------------------------------
This looks like a duplicate of https://issues.apache.org/jira/browse/SPARK-24864. Please see the discussion there. Basically Hive and Spark are two different systems and follow a different scheme to compute auto generated column names. We should be using aliases in the view definition to make it runnable from spark.
Thank you.
> Views without column names created by Hive are not readable by Spark
> --------------------------------------------------------------------
>
> Key: SPARK-25833
> URL: https://issues.apache.org/jira/browse/SPARK-25833
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.3.2
> Reporter: Chenxiao Mao
> Priority: Major
>
> A simple example to reproduce this issue.
> create a view via Hive CLI:
> {code:sql}
> hive> CREATE VIEW v1 AS SELECT * FROM (SELECT 1) t1
> {code}
> query that view via Spark
> {code:sql}
> spark-sql> select * from v1;
> Error in query: cannot resolve '`t1._c0`' given input columns: [1]; line 1 pos 7;
> 'Project [*]
> +- 'SubqueryAlias v1, `default`.`v1`
> +- 'Project ['t1._c0]
> +- SubqueryAlias t1
> +- Project [1 AS 1#41]
> +- OneRowRelation$
> {code}
> Check the view definition:
> {code:sql}
> hive> desc extended v1;
> OK
> _c0 int
> ...
> viewOriginalText:SELECT * FROM (SELECT 1) t1,
> viewExpandedText:SELECT `t1`.`_c0` FROM (SELECT 1) `t1`
> ...
> {code}
> _c0 in above view definition is automatically generated by Hive, which is not recognizable by Spark.
> see [Hive LanguageManual|https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=30746446&navigatingVersions=true#LanguageManualDDL-CreateView] for more details:
> {quote}If no column names are supplied, the names of the view's columns will be derived automatically from the defining SELECT expression. (If the SELECT contains unaliased scalar expressions such as x+y, the resulting view column names will be generated in the form _C0, _C1, etc.)
> {quote}
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