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From "Paul Rogers (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-5830) Resolve regressions to MapR DB from DRILL-5546
Date Sat, 30 Sep 2017 01:10:00 GMT

    [ https://issues.apache.org/jira/browse/DRILL-5830?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16186768#comment-16186768
] 

Paul Rogers commented on DRILL-5830:
------------------------------------

DRILL-5706 described a problem that we tried to fix with DRILL-5546. However, the problem
was not in the HBase storage plugin at all; instead it is in the unordered receiver (see DRILL-5826.)

Empty regions have the schema (row_key, cf{}) where cf is a column family. Non-empty regions
have the schema (row_key, cf{e0}) where e0 is a column within cf. The unordered receiver treated
these schemas as identical, removing the e0 column if it sees the empty batch first.

By fixing the unordered receiver, the original HBase problem disappears because the rest of
the code now properly handles the empty batches produced by empty regions. That is, the other
fixes from DRILL-5546 already solved the issue; we didn't need to change HBase for a solution;
instead we just needed to add one more fix for the unordered receiver.

(Note that all receivers would have the same issue and the fix in DRILL-5826 will address
all receivers.

> 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.



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