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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-5660) Drill 1.10 queries fail due to Parquet Metadata "corruption" from DRILL-3867
Date Fri, 21 Jul 2017 07:21:02 GMT

    [ https://issues.apache.org/jira/browse/DRILL-5660?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16095895#comment-16095895
] 

ASF GitHub Bot commented on DRILL-5660:
---------------------------------------

Github user arina-ielchiieva commented on a diff in the pull request:

    https://github.com/apache/drill/pull/877#discussion_r128698268
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/Metadata.java
---
    @@ -1851,9 +1922,73 @@ private static String relativize(String baseDir, String childPath)
{
               .relativize(fullPathWithoutSchemeAndAuthority.toUri()));
           if (relativeFilePath.isAbsolute()) {
             throw new IllegalStateException(String.format("Path %s is not a subpath of %s.",
    -            basePathWithoutSchemeAndAuthority.toUri().toString(), fullPathWithoutSchemeAndAuthority.toUri().toString()));
    +            basePathWithoutSchemeAndAuthority.toUri().getPath(), fullPathWithoutSchemeAndAuthority.toUri().getPath()));
    +      }
    +      return relativeFilePath.toUri().getPath();
    +    }
    +  }
    +
    +  /**
    +   * Supported metadata versions.
    +   * <p>
    +   * Note: keep them synchronized with {@link ParquetTableMetadataBase} versions
    +   */
    +  public static class MetadataVersion {
    --- End diff --
    
    1. Since this class is used in  other classes, I suggest we factor out as separate class.
This class has too many inner classes.
    2. It's not an enum, in this case name should be plural - `MetadataVersions`.


> Drill 1.10 queries fail due to Parquet Metadata "corruption" from DRILL-3867
> ----------------------------------------------------------------------------
>
>                 Key: DRILL-5660
>                 URL: https://issues.apache.org/jira/browse/DRILL-5660
>             Project: Apache Drill
>          Issue Type: Bug
>    Affects Versions: 1.11.0
>            Reporter: Paul Rogers
>            Assignee: Vitalii Diravka
>
> Drill recently accepted a PR for the following bug:
> DRILL-3867: Store relative paths in metadata file
> This PR turned out to have a flaw which affects version compatibility.
> The DRILL-3867 PR changed the format of Parquet metadata files to store relative paths.
All Drill servers after that PR create files with relative paths. But, the version number
of the file is unchanged, so that older Drillbits don't know that they can't understand the
file.
> Instead, if an older Drill tries to read the file, queries fail left and right. Drill
will resolve the paths, but does so relative to the user's HDFS home directory, which is wrong.
> What should have happened is that we should have bumped the parquet metadata file version
number so that older Drillbits can’t read the file. This ticket requests that we do that.
> Now, one could argue that the lack of version number change is fine. Once a user upgrades
Drill, they won't use an old Drillbit. But, things are not that simple:
> * A developer tests a branch based on a pre-DRILL-3867 build on a cluster in which metadata
files have been created by a post-DRILL-3867 build. (This has already occurred multiple times
in our shop.)
> * A user tries to upgrade to Drill 1.11, finds an issue, and needs to roll back to Drill
1.10. Doing so will cause queries to fail due to seemingly-corrupt metadata files.
> * A user tries to do a rolling upgrade: running 1.11 on some servers, 1.10 on others.
Once a 1.11 server is installed, the metadata is updated ("corrupted" from the perspective
of 1.10) and queries fail.
> Standard practice in this scenario is to:
> * Bump the file version number when the file format changes, and
> * Software refuses to read files with a version newer than the software was designed
for.
> Of course, it is highly desirable that newer servers read old files, but that is not
the issue here.



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