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From "Alex Behm (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-5483: Automatically disable codegen for small queries
Date Fri, 23 Jun 2017 18:44:45 GMT
Alex Behm has posted comments on this change.

Change subject: IMPALA-5483: Automatically disable codegen for small queries
......................................................................


Patch Set 3:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/7153/3//COMMIT_MSG
Commit Message:

PS3, Line 15: a plan node
> Those are good points. I've come around and think this optimization makes s
I ran some experiments to test the effects of disabling codegen. I tried plans with scans,
aggregations, top-n, union, joins and combinations of them with simple as well as complex
expressions in various places. I used test tables with 50k and 150k rows.

Summary: Even with the 150k rows table, I was not able to find a single scenario where the
codegen'd query ran faster. Most of the time the non-codegend query ran 2x faster.

So I'm thinking the 50k value is pretty conservative, i.e. safe.


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Gerrit-MessageType: comment
Gerrit-Change-Id: I273bcee58641f5b97de52c0b2caab043c914b32e
Gerrit-PatchSet: 3
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Tim Armstrong <tarmstrong@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.behm@cloudera.com>
Gerrit-Reviewer: Juan Yu <jyu@cloudera.com>
Gerrit-Reviewer: Michael Ho
Gerrit-Reviewer: Michael Ho <kwho@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <tarmstrong@cloudera.com>
Gerrit-HasComments: Yes

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