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From "Alex Behm (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-4787: Optimize APPX MEDIAN() memory usage
Date Sat, 18 Feb 2017 01:53:21 GMT
Alex Behm has posted comments on this change.

Change subject: IMPALA-4787: Optimize APPX_MEDIAN() memory usage
......................................................................


Patch Set 2:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/6025/2/be/src/exprs/aggregate-functions-ir.cc
File be/src/exprs/aggregate-functions-ir.cc:

PS2, Line 1024: new_size 
> Queries with a large number buckets will run out of memory much quicker tha
2x works for me but:

For buckets with many samples you spend more time reallocating, and the peak memory consumption
can be higher (space for 1.5 * MAX_NUM_SAMPLES).

See the experiment Taras posted in the commit msg. I'm fine with the 2x behavior, just pointing
out the tradeoffs.


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Gerrit-MessageType: comment
Gerrit-Change-Id: I99adaad574d4fb0a3cf38c6cbad8b2a23df12968
Gerrit-PatchSet: 2
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Taras Bobrovytsky <tbobrovytsky@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.behm@cloudera.com>
Gerrit-Reviewer: Marcel Kornacker <marcel@cloudera.com>
Gerrit-Reviewer: Matthew Jacobs <mj@cloudera.com>
Gerrit-Reviewer: Mostafa Mokhtar <mmokhtar@cloudera.com>
Gerrit-Reviewer: Taras Bobrovytsky <tbobrovytsky@cloudera.com>
Gerrit-HasComments: Yes

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