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From "Alex Behm (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-4923: reduce memory transfer for selective scans
Date Wed, 24 May 2017 21:50:59 GMT
Alex Behm has posted comments on this change.

Change subject: IMPALA-4923: reduce memory transfer for selective scans
......................................................................


Patch Set 3:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/6949/3/be/src/exec/parquet-scratch-tuple-batch.h
File be/src/exec/parquet-scratch-tuple-batch.h:

Line 102:     ++num_output_batches;
> Turns out it's the incorrect thing to do (found a bug in testing by test_me
I think the idea was right, but the code wasn't quite implementing the idea (sorry for the
distraction). If we increment the non-empty output batches at the end and modify the check
to non_empty_output_batches > 0, then I think it can work.

However, even that is suboptimal because what we really want to count are the non-compacted
output batches because those are they only ones can still reference the tuple mem.

Anyway, seems easy to forget a case and break this code, so let's worry about that potential
improvement later.


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Gerrit-MessageType: comment
Gerrit-Change-Id: I3773dc63c498e295a2c1386a15c5e69205e747ea
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: Dan Hecht <dhecht@cloudera.com>
Gerrit-Reviewer: Michael Ho <kwho@cloudera.com>
Gerrit-Reviewer: Mostafa Mokhtar <mmokhtar@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <tarmstrong@cloudera.com>
Gerrit-HasComments: Yes

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