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From "Sailesh Mukil (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] PREVIEW: IMPALA-2550 Introduce query-wide execution context.
Date Fri, 29 Jul 2016 20:42:54 GMT
Sailesh Mukil has posted comments on this change.

Change subject: PREVIEW: IMPALA-2550 Introduce query-wide execution context.
......................................................................


Patch Set 3:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/3817/3/be/src/runtime/query-exec-state.cc
File be/src/runtime/query-exec-state.cc:

PS3, Line 72: QueryExecMgr::ScopedQueryExecStateRef s(*query_exec_mgr, this);
Bug: I would have to call GetQES(query_ctx_.query_id) before this line to increment the ref
count (as the lock governing atomic increase/decrease of the ref count is the QueryExecMgr
wide query_exec_state_map_lock_ itself; which means only one thread across all queries can
get a single QES at a given time).

This seems really messy and can be completely avoided by using shared pointers. With shared
pointers, during object destruction, I could hold the object level lock while removing the
QES from the query_exec_state_map_.

Now, since the map contains a unique_ptr, I cannot hold an object level lock while removing
the QES object from the map.


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Gerrit-MessageType: comment
Gerrit-Change-Id: I892091d6401acb2ea91ccb1623af54c6f9635e6c
Gerrit-PatchSet: 3
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Sailesh Mukil <sailesh@cloudera.com>
Gerrit-Reviewer: Sailesh Mukil <sailesh@cloudera.com>
Gerrit-HasComments: Yes

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