Zoltan Borok-Nagy has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/11694 )

Change subject: IMPALA-7644: Hide Parquet page index writing with feature flag
......................................................................


Patch Set 2:

(3 comments)

Thanks for the comments!
I'm running ASAN tests currently just in case, so please postpone GVO until 
it's finished.

http://gerrit.cloudera.org:8080/#/c/11694/2//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/11694/2//COMMIT_MSG@8
PS2, Line 8:
> Can you mention somehow that the original was reverted, and this commits ad
Added a sentence about it.


http://gerrit.cloudera.org:8080/#/c/11694/2//COMMIT_MSG@18
PS2, Line 18: custom_cluset
> nit: typo
Done


http://gerrit.cloudera.org:8080/#/c/11694/2/be/src/exec/hdfs-parquet-table-writer.cc
File be/src/exec/hdfs-parquet-table-writer.cc:

http://gerrit.cloudera.org:8080/#/c/11694/2/be/src/exec/hdfs-parquet-table-writer.cc@705
PS2, Line 705: num_data_pages_
> I agree, that would simplify things substantially. When you do this, can yo
DataPage is not POD, but since we never set parquet::Statistics for the 
DataPageHeader it's ctor and dtor shouldn't do much.

I did some perf measurements locally. I did a release build and ran the 
following statement on a single-node cluster:

 create table lineitem stored as parquet as
 (select * from tpch.lineitem);

Then I compared the profiles with and without 'num_data_pages_'. I couldn't 
find any significant difference, because it seems that the effect of this 
change is smaller than the variance of the measurements. In fact, the version 
without 'num_data_pages_' was even faster a bit.

I'm calling clear() since it is more straightforward and now I'm sure enough 
about that it won't affect the capacity.



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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Ib4a9098a2085a385351477c715ae245d83bf1c72
Gerrit-Change-Number: 11694
Gerrit-PatchSet: 2
Gerrit-Owner: Zoltan Borok-Nagy <[email protected]>
Gerrit-Reviewer: Csaba Ringhofer <[email protected]>
Gerrit-Reviewer: Impala Public Jenkins <[email protected]>
Gerrit-Reviewer: Lars Volker <[email protected]>
Gerrit-Reviewer: Zoltan Borok-Nagy <[email protected]>
Gerrit-Comment-Date: Wed, 17 Oct 2018 15:33:36 +0000
Gerrit-HasComments: Yes

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