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From "Tim Armstrong (Code Review)" <>
Subject [Impala-ASF-CR] IMPALA-4037,IMPALA-4038: fix locking during query cancellation
Date Wed, 21 Sep 2016 23:59:51 GMT
Tim Armstrong has posted comments on this change.

Change subject: IMPALA-4037,IMPALA-4038: fix locking during query cancellation

Patch Set 6:

File be/src/runtime/coordinator.h:

PS6, Line 246: during
> what does this mean? while making RPCs? while servicing RPCs?
while making - Done
File be/src/service/

Line 220:   return child_queries_thread_.get();
> what does holding the lock here prevent? (related to my question about allo
I was generally just trying to keep the locking rules simple and conservative (i.e. grab the
lock when touching the state). I removed the locking and added justifications for why its
safe. I'm not concerned about the correctness here but it may get tricky if we add any additional
File be/src/service/child-query.h:

PS6, Line 161:  by joining
             :   /// 'child_queries_thread_'.
> you should explain this without talking about private members.
Just deleted that clause.

Line 167:   Status WaitForAll(std::vector<ChildQuery*>* completed_queries);
> can this be called by concurrently with ExecAsync() or is that not allowed?
Nope, documented it.

PS6, Line 170: and the execution thread has exited
> what does this really mean to the caller? that it can destroy the object? s
I mentioned this in the class comment but will also mention here and in WaitForAll.

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Gerrit-MessageType: comment
Gerrit-Change-Id: Ibe3024803e03595ee69c47759b58e8443d7bd167
Gerrit-PatchSet: 6
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Tim Armstrong <>
Gerrit-Reviewer: Alex Behm <>
Gerrit-Reviewer: Dan Hecht <>
Gerrit-Reviewer: Henry Robinson <>
Gerrit-Reviewer: Tim Armstrong <>
Gerrit-HasComments: Yes

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