[jira] [Commented] (SPARK-21338) AggregatedDialect doesn't override isCascadingTruncateTable() method

["Apache Spark (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-21338?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16169143#comment-16169143 ] 

Apache Spark commented on SPARK-21338:
--------------------------------------

User 'huaxingao' has created a pull request for this issue:
https://github.com/apache/spark/pull/19256

> AggregatedDialect doesn't override isCascadingTruncateTable() method
> --------------------------------------------------------------------
>
>                 Key: SPARK-21338
>                 URL: https://issues.apache.org/jira/browse/SPARK-21338
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 2.1.0, 2.1.1
>            Reporter: Ostap Gonchar
>
> org.apache.spark.sql.jdbc.JdbcDialect's method:
> *def isCascadingTruncateTable(): Option[Boolean] = None*
> is not overriden in org.apache.spark.sql.jdbc.AggregatedDialect class.
> Because of this issue - *+when you add  more than one dialect Spark doesn't truncate table because isCascadingTruncateTable always returns default None for Aggregated Dialect+*.
> Can be tracked when you write dataset in jdbc mode with SaveMode.Overwrite and extra JdbcDialect added via JdbcDialects.registerDialect(...); method.
> Then inside of org.apache.spark.sql.execution.datasources.jdbc.JdbcRelationProvider on line 65 in createRelation method it will never get to line 67 even if isTruncate returns true.
> It will only get inside if you have one JdbcDialect and AggregatedDialect is not used.
> Fix would be to overrite this method in AggregatedDialect and also to reduce value (I guess with and clause same as in overriden getHandle method) e.g. 
> override def isCascadingTruncateTable(): Option[Boolean]=
>     Some(dialects.map(_.isCascadingTruncateTable()).reduce(_ && _))



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