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https://issues.apache.org/jira/browse/DRILL-5830?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16190817#comment-16190817
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ASF GitHub Bot commented on DRILL-5830:
---------------------------------------
Github user paul-rogers commented on the issue:
https://github.com/apache/drill/pull/968
Thanks for the explanation! Bugs in the code are always a concern, but I
personally prefer to fix them rather than write more code that tries to work
around potential, unknown bugs in other code. (Working around known bugs is, of
course, part of the game.)
Sounds like we'll need to test the MapR-DB case for the conditions you
identified; that will tell is if the HBase solution (which seems to work now)
can also be applied to MapR DB.
> Resolve regressions to MapR DB from DRILL-5546
> ----------------------------------------------
>
> Key: DRILL-5830
> URL: https://issues.apache.org/jira/browse/DRILL-5830
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.12.0
> Reporter: Paul Rogers
> Assignee: Paul Rogers
> Fix For: 1.12.0
>
>
> DRILL-5546 added a number of fixes for empty batches. One part of the fix was
> for HBase. Key changes:
> * Add code to expand wildcards in the planner. (i.e. SELECT *)
> * Remove support for wildcards in the HBase record reader.
> As noted in DRILL-5775, this change had the effect of breaking support for
> MapR-DB binary (which is API compatible with HBase.) DRILL-5775 does this by
> expanding wildcards in the planner for MapR DB as was done for HBase in
> DRILL-5546.
> Unfortunately, this change introduced other regressions into the code as
> described by DRILL-5706.
> Investigation of those issues revealed that we should back out the original
> DRILL-5546 changes and go down a different route.
> As it turns out, HBase already had a project push-down rule that expanded
> wildcards. However, that rule didn't work correctly some of the time.
> DRILL-5546 fixed that bug, ensuring that wildcards are expanded (at least in
> the cases tested for this ticket.)
> The actual issue turned out to be a bug in the {{RecordBatchLoader}} class
> which did not consider map contents when detecting schema change. As a
> result, results like (row_key, cf\{}) were treated the same as (row_key,
> cf\{mycol}) and the actual data colums were discarded, but randomly depending
> on batch arrival order.
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