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https://issues.apache.org/jira/browse/SPARK-4293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14201670#comment-14201670
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Apache Spark commented on SPARK-4293:
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User 'ueshin' has created a pull request for this issue:
https://github.com/apache/spark/pull/3150
> Make Cast be able to handle complex types.
> ------------------------------------------
>
> Key: SPARK-4293
> URL: https://issues.apache.org/jira/browse/SPARK-4293
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Reporter: Takuya Ueshin
>
> Inserting data of type including {{ArrayType.containsNull == false}} or
> {{MapType.valueContainsNull == false}} or
> {{StructType.fields.exists(_.nullable == false)}} into Hive table will fail
> because {{Cast}} inserted by {{HiveMetastoreCatalog.PreInsertionCasts}} rule
> of {{Analyzer}} can't handle these types correctly.
> Complex type cast rule proposal:
> * Cast for non-complex types should be able to cast the same as before.
> * Cast for {{ArrayType}} can evaluate if
> ** Element type can cast
> ** Nullability rule doesn't break
> * Cast for {{MapType}} can evaluate if
> ** Key type can cast
> ** Nullability for casted key type is {{false}}
> ** Value type can cast
> ** Nullability rule for value type doesn't break
> * Cast for {{StructType}} can evaluate if
> ** The field size is the same
> ** Each field can cast
> ** Nullability rule for each field doesn't break
> * The nested structure should be the same.
> Nullability rule:
> * If the casted type is {{nullable == true}}, the target nullability should
> be {{true}}
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