[jira] [Commented] (PARQUET-899) Add metadata field describing the application that wrote the file

["Nandor Kollar (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PARQUET-899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16280465#comment-16280465 ] 

Nandor Kollar commented on PARQUET-899:
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[~zi] isn't {{org.apache.parquet.hadoop.metadata.FileMetaData#createdBy}} used for this purpose? Also, this class has a {{Map<String, String> keyValueMetaData}} variable too, applications can store arbitrary metadata there (like version number).

> Add metadata field describing the application that wrote the file
> -----------------------------------------------------------------
>
>                 Key: PARQUET-899
>                 URL: https://issues.apache.org/jira/browse/PARQUET-899
>             Project: Parquet
>          Issue Type: Improvement
>            Reporter: Zoltan Ivanfi
>
> Although the Parquet library should behave the same regardless of what application uses it, occasionally serious interoperability bugs are introduced in specific applications. For example, data written by a specific application may be unnecessarily adjusted or the calculated statistics may be invalid (both actual problems).
> Unfortunately, currently it is not possible to recognize Parquet files affected by application problems because the metadata does not contain any information about the application using the Parquet library. (The name and version number of the Parquet library is recorded, but that only has limited use, because apart from Impala, the most widespread Parquet writers all use the same Java library.)
> To allow creating workarounds for future known issues, we should introduce new metadata fields that applications can populate. The simplest approach is to have one field for the application name and another for its version number. A more sophisticated approach suggested by [~julienledem] could also reference a list of earlier issues that are known to be fixed in the application that wrote the Parquet file.



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