[jira] [Commented] (PARQUET-1950) Define core features / compliance level

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PARQUET-1950?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17726838#comment-17726838 ] 

ASF GitHub Bot commented on PARQUET-1950:
-----------------------------------------

emkornfield commented on code in PR #164:
URL: https://github.com/apache/parquet-format/pull/164#discussion_r1208103637


##########
src/main/thrift/parquet.thrift:
##########
@@ -1041,6 +1041,13 @@ struct FileMetaData {
    * Used only in encrypted files with plaintext footer. 
    */ 
   9: optional binary footer_signing_key_metadata
+
+  /**
+   * This field might be set with the version number of a parquet-format release
+   * if this file is created by using only the features listed in the related
+   * list of core features. See CoreFeatures.md for details.

Review Comment:
   FWIW, Impala reads this field and fails if it is 2 (https://issues.apache.org/jira/browse/IMPALA-11838?filter=-2)





> Define core features / compliance level
> ---------------------------------------
>
>                 Key: PARQUET-1950
>                 URL: https://issues.apache.org/jira/browse/PARQUET-1950
>             Project: Parquet
>          Issue Type: New Feature
>          Components: parquet-format
>            Reporter: Gabor Szadovszky
>            Assignee: Gabor Szadovszky
>            Priority: Major
>
> Parquet format is getting more and more features while the different implementations cannot keep the pace and left behind with some features implemented and some are not. In many cases it is also not clear if the related feature is mature enough to be used widely or more an experimental one.
> These are huge issues that makes hard ensure interoperability between the different implementations.
> The following idea came up in a [discussion|https://lists.apache.org/thread.html/rde5cba8443487bccd47593ddf5dfb39f69c729d260165cb936a1a289%40%3Cdev.parquet.apache.org%3E]. Create a now document in the parquet-format repository that lists the "core features". This document is versioned by the parquet-format releases. This way a certain version of "core features" defines a level of compatibility between the different implementations. This version number can be written to a new field (e.g. complianceLevel) in the footer. If an implementation writes a file with a version in the field it must implement all the related "core features" (read and write) and must not use any other features at write because it makes the data unreadable by another implementation if only the same level of "core features" are implemented.
> For example if we have encoding A listed in the version 1 "core features" but encoding B is not then at "complianceLevel = 1" we can use encoding A but we cannot use encoding B because it would make the related data unreadable.



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