Paul Rogers created DRILL-5660:
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Summary: 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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