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https://issues.apache.org/jira/browse/PARQUET-1950?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17277847#comment-17277847
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ASF GitHub Bot commented on PARQUET-1950:
-----------------------------------------
gszadovszky commented on a change in pull request #164:
URL: https://github.com/apache/parquet-format/pull/164#discussion_r569260891
##########
File path: 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:
It doesn't sound good. It means that we are using a required field for
different purposes. Because it is required we cannot deprecate it easily.
parquet-mr does not read this field only writes `1` all the time. What does
parquet-cpp does with this value at the read path?
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> 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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