Tim Armstrong has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/10058 )

Change subject: IMPALA-6847: work around high memory estimates for AC
......................................................................


Patch Set 6:

(2 comments)

http://gerrit.cloudera.org:8080/#/c/10058/2//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/10058/2//COMMIT_MSG@19
PS2, Line 19: the planner prevents runaway memory consumption. This is still
> Fine with me.
Done


http://gerrit.cloudera.org:8080/#/c/10058/6/be/src/scheduling/query-schedule.cc
File be/src/scheduling/query-schedule.cc:

http://gerrit.cloudera.org:8080/#/c/10058/6/be/src/scheduling/query-schedule.cc@195
PS6, Line 195:     per_host_mem = min(query_option_memory_limit, 
request_.per_host_mem_estimate);
> what's the advantage to introducing this special case, rather than just cli
The frontend set mem_limit so we need a special case here regardless to avoid 
going down the normal mem_limit code path. The intent of the option is to 
influence admission control behaviour so this seemed like the most direct way 
to express the intended behaviour.

In some ways this code code change would be more cohesive if all the logic was 
confined to the scheduler/admission controller. The reason I didn't do that is 
that there's no precedent for modifying query options in the scheduler and I 
didn't think it was worth adding another phase where they were mutable (since 
that adds some potential for introducing bugs).



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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Ia5fc32a507ad0f00f564dfe4f954a829ac55d14e
Gerrit-Change-Number: 10058
Gerrit-PatchSet: 6
Gerrit-Owner: Tim Armstrong <tarmstr...@cloudera.com>
Gerrit-Reviewer: Bikramjeet Vig <bikramjeet....@cloudera.com>
Gerrit-Reviewer: Dan Hecht <dhe...@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <tarmstr...@cloudera.com>
Gerrit-Comment-Date: Mon, 16 Apr 2018 18:49:29 +0000
Gerrit-HasComments: Yes

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