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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 Thu, 13 Jul 2017 18:57:00 GMT

    [ https://issues.apache.org/jira/browse/DRILL-5660?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16086221#comment-16086221
] 

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

GitHub user vdiravka opened a pull request:

    https://github.com/apache/drill/pull/877

    DRILL-5660: Drill 1.10 queries fail due to Parquet Metadata "corrupti…

    …on" from DRILL-3867
    
    - bump up metadata file version to v3_1;
    - ignoring of unknown metadata version (for example metadata generated from future versions
of drill);
    - adding removing "%20" symbols from path.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/vdiravka/drill DRILL-5660

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/drill/pull/877.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #877
    
----
commit 0d121022e16b5d316c357207706cc1454b77a5a0
Author: Vitalii Diravka <vitalii.diravka@gmail.com>
Date:   2017-07-12T22:12:00Z

    DRILL-5660: Drill 1.10 queries fail due to Parquet Metadata "corruption" from DRILL-3867
    
    - bump up metadata file version to v3_1;
    - ignoring of unknown metadata version (for example metadata generated from future versions
of drill);
    - adding removing "%20" symbols from path.

----


> 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
>             Fix For: 1.11.0
>
>
> 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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