[jira] [Commented] (IMPALA-3902) Multi-threaded query execution

["ASF subversion and git services (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/IMPALA-3902?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17072148#comment-17072148 ] 

ASF subversion and git services commented on IMPALA-3902:
---------------------------------------------------------

Commit ab7e209d1bf8f8d61e092b6de9078c0d2e8c657d in impala's branch refs/heads/master from Tim Armstrong
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=ab7e209 ]

IMPALA-9099: allow mt_dop for joins without feature flag

This allows running *any* read-only query with mt_dop > 0.
Before this patch, no joins were allowed with mt_dop > 0.

Previous patches, particularly IMPALA-9156, added significantly
more code coverage for multithreading+joins. It should be safe to
allow enabling on a query-by-query basis. Many improvements are
still planned - see IMPALA-3902. So behaviour and performance
characteristics of mt_dop > 0 with more complex plans and joins
will continue to change.

Testing:
Updated the mt_dop validation tests and remove redundant planner test
that doesn't provide much additional coverage of the validation
support.

Ran exhaustive tests.

Change-Id: I9c6566abb239db0e775f2beaa25a62c36313cd6f
Reviewed-on: http://gerrit.cloudera.org:8080/15545
Reviewed-by: Impala Public Jenkins <im...@cloudera.com>
Tested-by: Impala Public Jenkins <im...@cloudera.com>


> Multi-threaded query execution
> ------------------------------
>
>                 Key: IMPALA-3902
>                 URL: https://issues.apache.org/jira/browse/IMPALA-3902
>             Project: IMPALA
>          Issue Type: Epic
>          Components: Backend
>    Affects Versions: Impala 2.6.0
>            Reporter: Marcel Kinard
>            Assignee: Tim Armstrong
>            Priority: Minor
>              Labels: multithreading
>
> Currently, a single query fragment is run in a quasi-single threaded manner on a node: the scanners are run in multiple threads, but all other operators (joins, aggregation) are run in the main thread.
> The goal is to add multi-threaded execution on a single node by running multiple fragment instances (each of which runs in a single thread).



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