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https://issues.apache.org/jira/browse/PARQUET-251?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14495488#comment-14495488
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Alex Levenson commented on PARQUET-251:
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Yes, my point was that Binary is just a wrapper, and the decision to copy / not 
copy seems like it should be handled outside the wrapper.

So maybe all that is needed is to add a helper method to Binary called 
copyToByteArray()?
Though toByteArray() usually make a copy, so maybe we should just make that the 
contract?

Or just some consistency around ownership? If you pass a byte[] to a Binary, 
should we say the contract is that ownership has passed to the Binary and you 
shouldn't mutate it any more?

> Binary column statistics error when reuse byte[] among rows
> -----------------------------------------------------------
>
>                 Key: PARQUET-251
>                 URL: https://issues.apache.org/jira/browse/PARQUET-251
>             Project: Parquet
>          Issue Type: Bug
>          Components: parquet-mr
>    Affects Versions: 1.6.0
>            Reporter: Yijie Shen
>            Priority: Blocker
>
> I think it is a common practice when inserting table data as parquet file, 
> one would always reuse the same object among rows, and if a column is byte[] 
> of fixed length, the byte[] would also be reused. 
> If I use ByteArrayBackedBinary for my byte[], the bug occurs: All of the row 
> groups created by a single task would have the same max & min binary value, 
> just as the last row's binary content.
> The reason is BinaryStatistic just keep max & min as parquet.io.api.Binary 
> references, since I use ByteArrayBackedBinary for byte[], the real content of 
> max & min would always point to the reused byte[], therefore the latest row's 
> content.
> Does parquet declare somewhere that the user shouldn't reuse byte[] for 
> Binary type?  If it doesn't, I think it's a bug and can be reproduced by 
> [Spark SQL's RowWriteSupport 
> |https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/parquet/ParquetTableSupport.scala#L353-354]
> The related Spark JIRA ticket: 
> [SPARK-6859|https://issues.apache.org/jira/browse/SPARK-6859]



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