Joe McDonnell has posted comments on this change. ( http://gerrit.cloudera.org:8080/16020 )
Change subject: IMPALA-9318: Add admission control setting to cap MT_DOP ...................................................................... Patch Set 3: (4 comments) http://gerrit.cloudera.org:8080/#/c/16020/3//COMMIT_MSG Commit Message: http://gerrit.cloudera.org:8080/#/c/16020/3//COMMIT_MSG@16 PS3, Line 16: unlimited MT_DOP > do you mean there is no limit applied like with negative value? Yes, changed this to say that it defaults to -1 which applies no limit http://gerrit.cloudera.org:8080/#/c/16020/3/be/src/service/impala-server.cc File be/src/service/impala-server.cc: http://gerrit.cloudera.org:8080/#/c/16020/3/be/src/service/impala-server.cc@914 PS3, Line 914: EnforceMaxMtDop > since the config values can change while the query is in admission controll A couple thoughts: I think we want to avoid having a difference in behavior when you change the policy vs when it is stable. In other words, if we are usually downgrading queries, it is harder for users to understand if we switch to throwing an error for this transitional situation. I think it is ok for us to say that the policy is evaluated before planning and does not get updated after that. We wouldn't be able to modify queued queries, but I think that is a behavior that administrators can work with. I updated the commit comment to mention this behavior. Is this ok? http://gerrit.cloudera.org:8080/#/c/16020/3/common/thrift/ImpalaInternalService.thrift File common/thrift/ImpalaInternalService.thrift: http://gerrit.cloudera.org:8080/#/c/16020/3/common/thrift/ImpalaInternalService.thrift@594 PS3, Line 594: 26: optional i32 overridden_mt_dop_value = -1; > Doesn't matter too much, but would probably be more consistent with other o Good point, changed this to use that http://gerrit.cloudera.org:8080/#/c/16020/3/testdata/workloads/functional-query/queries/QueryTest/max-mt-dop.test File testdata/workloads/functional-query/queries/QueryTest/max-mt-dop.test: http://gerrit.cloudera.org:8080/#/c/16020/3/testdata/workloads/functional-query/queries/QueryTest/max-mt-dop.test@7 PS3, Line 7: select count(*) from tpch.lineitem; > tpch_parquet.lineitem would also be significantly faster, since it turns in I think I was trying to be smart and avoid planner downgrades, but it actually doesn't matter. The settings would be the same regardless of the query complexity. Switched this to "select 1" -- To view, visit http://gerrit.cloudera.org:8080/16020 To unsubscribe, visit http://gerrit.cloudera.org:8080/settings Gerrit-Project: Impala-ASF Gerrit-Branch: master Gerrit-MessageType: comment Gerrit-Change-Id: I3affb127a5dca517591323f2b1c880aa4b38badd Gerrit-Change-Number: 16020 Gerrit-PatchSet: 3 Gerrit-Owner: Joe McDonnell <[email protected]> Gerrit-Reviewer: Bikramjeet Vig <[email protected]> Gerrit-Reviewer: Impala Public Jenkins <[email protected]> Gerrit-Reviewer: Joe McDonnell <[email protected]> Gerrit-Reviewer: Tim Armstrong <[email protected]> Gerrit-Comment-Date: Fri, 05 Jun 2020 22:42:47 +0000 Gerrit-HasComments: Yes
