Lars Volker has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/11575 )

Change subject: IMPALA-6964: Track stats about column and page sizes in Parquet 
reader
......................................................................


Patch Set 10:

(7 comments)

http://gerrit.cloudera.org:8080/#/c/11575/10/be/src/exec/hdfs-scan-node-base.h
File be/src/exec/hdfs-scan-node-base.h:

http://gerrit.cloudera.org:8080/#/c/11575/10/be/src/exec/hdfs-scan-node-base.h@563
PS10, Line 563: multiple
nit: double word


http://gerrit.cloudera.org:8080/#/c/11575/10/be/src/exec/hdfs-scan-node-base.h@564
PS10, Line 564: updated
nit: typo


http://gerrit.cloudera.org:8080/#/c/11575/10/be/src/exec/hdfs-scan-node-base.h@565
PS10, Line 565:   boost::shared_mutex bytes_read_per_col_lock_;
Is it an option to collect the stats in the column readers and then pull them 
from there in StopAndFinalizeCounters instead? That would prevent us from 
having a lock.


http://gerrit.cloudera.org:8080/#/c/11575/10/be/src/exec/hdfs-scan-node-base.cc
File be/src/exec/hdfs-scan-node-base.cc:

http://gerrit.cloudera.org:8080/#/c/11575/10/be/src/exec/hdfs-scan-node-base.cc@901
PS10, Line 901:       
uncompressed_bytes_read_per_column_counter_->UpdateCounter(bytes_read.second.first);
Do we need to acquire the lock here, too? It we don't, can you add a comment to 
explain why?


http://gerrit.cloudera.org:8080/#/c/11575/10/be/src/exec/hdfs-scan-node-base.cc@945
PS10, Line 945:   auto bytes_read = bytes_read_per_col_.find(slot_id);
nit: in this case I'd mention the type in the name to prevent confusion, i.e. 
bytes_read_it = ...


http://gerrit.cloudera.org:8080/#/c/11575/10/be/src/exec/hdfs-scan-node-base.cc@947
PS10, Line 947:     lock_guard<boost::shared_mutex> 
bytes_read_per_col_guard(bytes_read_per_col_lock_);
It seems that unique_lock is the corresponding unique version of shared_lock. 
Is there a benefit in using shared_lock?

Can you add the namespace to the lock templates, too? Otherwise it's not clear 
whether we're using std:: or boost::.


http://gerrit.cloudera.org:8080/#/c/11575/5/tests/util/parse_util.py
File tests/util/parse_util.py:

http://gerrit.cloudera.org:8080/#/c/11575/5/tests/util/parse_util.py@137
PS5, Line 137:       example of how this method should be used:
> Done
I think it'd be nice to actually execute the example code. You could look for a 
suitable test where to add it, or just add the assert to this method.



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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: I322f9b324b6828df28e5caf79529085c43d7c817
Gerrit-Change-Number: 11575
Gerrit-PatchSet: 10
Gerrit-Owner: Sahil Takiar <[email protected]>
Gerrit-Reviewer: Impala Public Jenkins <[email protected]>
Gerrit-Reviewer: Lars Volker <[email protected]>
Gerrit-Reviewer: Sahil Takiar <[email protected]>
Gerrit-Comment-Date: Tue, 13 Nov 2018 20:28:11 +0000
Gerrit-HasComments: Yes

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