Zoltan Borok-Nagy has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/9381 )

Change subject: IMPALA-6542: Fix inconsistent write path of Parquet min/max 
statistics
......................................................................


Patch Set 2:

(3 comments)

http://gerrit.cloudera.org:8080/#/c/9381/1/be/src/exec/parquet-column-stats.inline.h
File be/src/exec/parquet-column-stats.inline.h:

http://gerrit.cloudera.org:8080/#/c/9381/1/be/src/exec/parquet-column-stats.inline.h@37
PS1, Line 37: std::is_floating_point<T>::value>
> I'm not sure I get this. I played around a little bit with putting is_float
If T is not a numeric type, then it can be a problem, e.g. you have the 
following code:

 template <typename T>
 void printer(const T& t) {
   if (is_floating_point<T>::value) {
     cout << fmax(t, t) << endl;
   } else {
     cout << "no" << endl;
   }
 }

As long as you invoke this function with numbers, your code compiles. But, when 
you invoke this function with T = std::string, you'll get a compiler error 
because there is no fmax() function that takes std::string as a parameter.

However, the C++17 constexpr ifs will enable these code structures.


http://gerrit.cloudera.org:8080/#/c/9381/2/testdata/workloads/functional-query/queries/QueryTest/parquet-stats.test
File testdata/workloads/functional-query/queries/QueryTest/parquet-stats.test:

http://gerrit.cloudera.org:8080/#/c/9381/2/testdata/workloads/functional-query/queries/QueryTest/parquet-stats.test@495
PS2, Line 495: # IMPALA-6527: NaN values lead to incorrect filtering.
> The following 3 tests were introduced with the read path fix. Do you think
Yeah I think you are right. I'll drop the equality test.
* 'val > 0' tests that the max filter doesn't reject the column chunk.
* 'van < 100' tests that the min filter doesn't reject the column chunk.
So, I keep these two.


http://gerrit.cloudera.org:8080/#/c/9381/2/testdata/workloads/functional-query/queries/QueryTest/parquet-stats.test@530
PS2, Line 530: nof
> nit: Typo or some abbreviation I don't know? :)
typo :)



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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I3957806948f7c661af4be5495f2ec92d1e9fc9d6
Gerrit-Change-Number: 9381
Gerrit-PatchSet: 2
Gerrit-Owner: Zoltan Borok-Nagy <borokna...@cloudera.com>
Gerrit-Reviewer: Gabor Kaszab <gaborkas...@cloudera.com>
Gerrit-Reviewer: Lars Volker <l...@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <tarmstr...@cloudera.com>
Gerrit-Reviewer: Zoltan Borok-Nagy <borokna...@cloudera.com>
Gerrit-Comment-Date: Thu, 22 Feb 2018 16:20:11 +0000
Gerrit-HasComments: Yes

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