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Date: Sat, 30 Sep 2017 01:05:00 +0000 (UTC)
From: "Paul Rogers (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (DRILL-5830) Resolve regressions to MapR DB from
 DRILL-5546
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archived-at: Sat, 30 Sep 2017 01:05:04 -0000


    [ https://issues.apache.org/jira/browse/DRILL-5830?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16186767#comment-16186767 ] 

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

The DRILL-5546 changes for HBase were based on the idea that the planner should expand wildcards. Yet, as it turns out, code to do that already existed in the HBase storage plugin in the form of a projection push-down rule. Therefore, the new code added in DRILL-5546 turns out to be redundant. (There do seem to be cases in which the projection push-down rule is not fired, but that is a separate issue.)

Backing out the HBase changes (only) for DRILL-5546 shows that wildcards are, in fact, expanded by the planner.

Since wildcard expansion already was in place before DRILL-5546, then wildcard expansion cannot, by itself, be the solution to the problems such as DRILL-5480. See below for the underlying problem.

> 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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