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https://issues.apache.org/jira/browse/SPARK-25391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16608750#comment-16608750
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Apache Spark commented on SPARK-25391:
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User 'seancxmao' has created a pull request for this issue:
https://github.com/apache/spark/pull/22343
> Make behaviors consistent when converting parquet hive table to parquet data
> source
> -----------------------------------------------------------------------------------
>
> Key: SPARK-25391
> URL: https://issues.apache.org/jira/browse/SPARK-25391
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.4.0
> Reporter: Chenxiao Mao
> Priority: Major
>
> parquet data source tables and hive parquet tables have different behaviors
> about parquet field resolution. So, when
> {{spark.sql.hive.convertMetastoreParquet}} is true, users might face
> inconsistent behaviors. The differences are:
> * Whether respect {{spark.sql.caseSensitive}}. Without SPARK-25132, both
> data source tables and hive tables do NOT respect
> {{spark.sql.caseSensitive}}. However data source tables always do
> case-sensitive parquet field resolution, while hive tables always do
> case-insensitive parquet field resolution no matter whether
> {{spark.sql.caseSensitive}} is set to true or false. SPARK-25132 let data
> source tables respect {{spark.sql.caseSensitive}} while hive serde table
> behavior is not changed.
> * How to resolve ambiguity in case-insensitive mode. Without SPARK-25132,
> data source tables do case-sensitive resolution and return columns with the
> corresponding letter cases, while hive tables always return the first matched
> column ignoring cases. SPARK-25132 let data source tables throw exception
> when there is ambiguity while hive table behavior is not changed.
> This ticket aims to make behaviors consistent when converting hive table to
> data source table.
> * The behavior must be consistent to do the conversion, so we skip the
> conversion in case-sensitive mode because hive parquet table always do
> case-insensitive field resolution.
> * In case-insensitive mode, when converting hive parquet table to parquet
> data source, we switch the duplicated fields resolution mode to ask parquet
> data source to pick the first matched field - the same behavior as hive
> parquet table - to keep behaviors consistent.
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