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From "Tim Armstrong (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-5483: Automatically disable codegen for small queries
Date Fri, 23 Jun 2017 17:52:58 GMT
Tim Armstrong 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
> My concern is about the false positive scenario where we disable_codegen be
I disagree that response time on small queries is always low. If there are complex expressions
or many joins the response time is often several seconds, or can actually be arbitrarily high.

I agree in general that it's hard to reason about when planner estimates will be accurate,
but this optimisation is a special case because it looks at the number of input rows to the
scans, where we can make stronger assumptions about accuracy.


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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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