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Posted to issues@drill.apache.org by "ASF GitHub Bot (JIRA)" <ji...@apache.org> on 2018/04/18 00:26:00 UTC
[jira] [Commented] (DRILL-6339) New option to disable TopN (for
testing Sort)
[ https://issues.apache.org/jira/browse/DRILL-6339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16441699#comment-16441699 ]
ASF GitHub Bot commented on DRILL-6339:
---------------------------------------
GitHub user Ben-Zvi opened a pull request:
https://github.com/apache/drill/pull/1219
DRILL-6339: Add a new option to disable TopN (for testing)
To allow simple testing of the External Sort operator (e.g., test spilling), we would like to use a query of the form: ".... ORDER BY ... LIMIT ... "; however the current planner unconditionally selects the TopN operator for such a query.
Solution: Introduce an internal option that can negate the planner's choice in this case. The implementation overrides the matches() method (default was returning true) in PushLimitToTopN , returning the new boolean option (default true) instead.
(The last 'true' in SystemOptionManager makes this option 'internal'). This new option was tested manually.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/Ben-Zvi/drill DRILL-6339
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/drill/pull/1219.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 #1219
----
commit 0c5bb6be7d62039dbd65e5fb06f949178bcd36eb
Author: Ben-Zvi <bb...@...>
Date: 2018-04-18T00:05:50Z
DRILL-6339: Add a new option to disable TopN (for testing)
----
> New option to disable TopN (for testing Sort)
> ---------------------------------------------
>
> Key: DRILL-6339
> URL: https://issues.apache.org/jira/browse/DRILL-6339
> Project: Apache Drill
> Issue Type: Improvement
> Components: Query Planning & Optimization
> Affects Versions: 1.13.0
> Reporter: Boaz Ben-Zvi
> Assignee: Boaz Ben-Zvi
> Priority: Minor
> Fix For: 1.14.0
>
>
> When a query uses ... ORDER BY ... LIMIT ..., the planner unconditionally picks the TopN operator to (efficiently) implement this order. This precludes an easy way to test the External Sort operator over a large dataset (e.g., test spilling).
> A new internal option to disable picking TopN (hence using the External Sort instead) would be useful for various testings. (And may be in other scenarios, like a bug found in the TopN).
>
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