Csaba Ringhofer has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/11731 )

Change subject: IMPALA-7698: Add centos support to bootstrap_system.
......................................................................


Patch Set 1:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/11731/1//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/11731/1//COMMIT_MSG@29
PS1, Line 29: I'm not yet clear on why the ORC library is choosing to open that 
time zone
            : file (which doesn't exist), but this change seems workable even 
with the test
            : failures.
About the ORC timezone issues:
tldr: ORC's timezone handling is likely to be broken in Impala so we should 
patch it in the toolchain

The ORC library implements its own IANA timezone handling to convert stored 
timestamps from UTC to local time + do something similar for min/max stats. The 
writer's timezone can be also stored in .orc files and used instead of local 
timezone.

Impala's and ORC library's timezone can be different because of several reasons:
- ORC's timezone is not overridden by env var TZ and query option timezone
- ORC uses a simpler way to detect the local timezone which may not work on 
some Linux distros (see TimezoneDatabase::LocalZoneName in Impala vs 
LOCAL_TIMEZONE in Orc)
- .orc files can use any time zone as writer's timezone and we cannot be sure 
that it will exist on the reader machine

My suggestion is to patch the ORC library in the toolchain and remove timezone 
handling (e.g. by always using UTC, maybe depending on a flag), as the way it 
is currently working is likely to be broken and is surely not consistent with 
the rest of Impala.

I am not sure how timezones could be handled correctly in Orc + Impala. If 
someone plans to work on it, I would gladly help in the integration to Impala.



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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Id54294d7607f51de87a9de373dcfc4a33f4bedf5
Gerrit-Change-Number: 11731
Gerrit-PatchSet: 1
Gerrit-Owner: Philip Zeyliger <[email protected]>
Gerrit-Reviewer: Csaba Ringhofer <[email protected]>
Gerrit-Reviewer: Impala Public Jenkins <[email protected]>
Gerrit-Reviewer: Joe McDonnell <[email protected]>
Gerrit-Reviewer: Laszlo Gaal <[email protected]>
Gerrit-Reviewer: Philip Zeyliger <[email protected]>
Gerrit-Comment-Date: Fri, 19 Oct 2018 16:03:08 +0000
Gerrit-HasComments: Yes

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