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From "Tim Armstrong (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-5347: Parquet scanner microoptimizations
Date Tue, 23 May 2017 18:14:39 GMT
Tim Armstrong has posted comments on this change.

Change subject: IMPALA-5347: Parquet scanner microoptimizations
......................................................................


Patch Set 5:

(2 comments)

http://gerrit.cloudera.org:8080/#/c/6950/5/be/src/exec/parquet-column-readers.cc
File be/src/exec/parquet-column-readers.cc:

Line 315:   /// Use __restrict__ so that the compiler knows that it is safe to cache member
> Just so I'm clear:
We compile with -fno-strict-alias so there's no type-based alias analysis at all - basically
anything can alias. ParquetLevelDecoder::cached_levels_ is also a problem.

I expanded the comment to be less hand-wavy.


Line 489:     uint8_t val_buf[sizeof(T)];
> Also needs aligning as T, right?
Seems like a good idea. I'm not sure if we really depend on it - generally we don't assume
that Tuples are actually aligned.


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Gerrit-MessageType: comment
Gerrit-Change-Id: I49ec523a65542fdbabd53fbcc4a8901d769e5cd5
Gerrit-PatchSet: 5
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Tim Armstrong <tarmstrong@cloudera.com>
Gerrit-Reviewer: Alex Behm <alex.behm@cloudera.com>
Gerrit-Reviewer: Jim Apple <jbapple-impala@apache.org>
Gerrit-Reviewer: Mostafa Mokhtar <mmokhtar@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <tarmstrong@cloudera.com>
Gerrit-Reviewer: anujphadke <aphadke@cloudera.com>
Gerrit-HasComments: Yes

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