Alexey Serbin has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/13666 )

Change subject: KUDU-2866. Optimize CFileSet::Iterator::FinishBatch
......................................................................


Patch Set 2:

(2 comments)

http://gerrit.cloudera.org:8080/#/c/13666/2//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/13666/2//COMMIT_MSG@16
PS2, Line 16: will only be prepared once
Most likely I'm missing something, but from breefly looking into the 
implementation, I don't see how this is guaranteed.  What if running some silly 
query like SELECT * FROM x WHERE col = a AND col = b?  Will column 'col' be 
prepared only once?  E.g., what if that code is called from 
MaterializingIterator::MaterializeBlock() twice?


http://gerrit.cloudera.org:8080/#/c/13666/2/src/kudu/tablet/cfile_set.cc
File src/kudu/tablet/cfile_set.cc:

http://gerrit.cloudera.org:8080/#/c/13666/2/src/kudu/tablet/cfile_set.cc@470
PS2, Line 470:   prepared_iters_.clear();
nit: does it make sense to add

  prepared_iters_.reserve(col_iters_.size());

?



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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I997fe832fdfa8d92fbbcb5d7c5bd4141e485b4f8
Gerrit-Change-Number: 13666
Gerrit-PatchSet: 2
Gerrit-Owner: Todd Lipcon <[email protected]>
Gerrit-Reviewer: Alexey Serbin <[email protected]>
Gerrit-Reviewer: Grant Henke <[email protected]>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Tidy Bot (241)
Gerrit-Comment-Date: Tue, 18 Jun 2019 21:23:33 +0000
Gerrit-HasComments: Yes

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