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mpp: Fix the crash or error when mpp generate empty task list. #31658

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merged 11 commits into from
Jan 14, 2022
Merged

mpp: Fix the crash or error when mpp generate empty task list. #31658

merged 11 commits into from
Jan 14, 2022

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LittleFall
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@LittleFall LittleFall commented Jan 13, 2022 •
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What problem does this PR solve?

Issue Number: close #31636

Problem Summary: apply may generate an empty range list, and then generate an empty mpp task list, but we don't handle it correctly.

What is changed and how it works?

handle the situation when mpp task list is empty.

Check List

Tests

  • Unit test
  • Integration test
    need add the original case to our intergration cases

Side effects

  • Performance regression: Consumes more CPU
  • Performance regression: Consumes more Memory
  • Breaking backward compatibility

Documentation

  • Affects user behaviors
  • Contains syntax changes
  • Contains variable changes
  • Contains experimental features
  • Changes MySQL compatibility

Release note

Fix the crash or error when generating an empty mpp task list.

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ti-chi-bot commented Jan 13, 2022 •
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[REVIEW NOTIFICATION]

This pull request has been approved by:

  • hanfei1991
  • windtalker

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@ti-chi-bot ti-chi-bot added do-not-merge/needs-linked-issue release-note-none Denotes a PR that doesn't merit a release note. size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels Jan 13, 2022
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sre-bot commented Jan 13, 2022

Please follow PR Title Format:

  • pkg [, pkg2, pkg3]: what is changed

Or if the count of mainly changed packages are more than 3, use

  • *: what is changed

After you have format title, you can leave a comment /run-check_title to recheck it

@LittleFall LittleFall changed the title Fix the crash when mpp balancer receive empty task list. copr: Fix the crash when mpp balancer receive empty task list. Jan 13, 2022
@ti-chi-bot ti-chi-bot added size/S Denotes a PR that changes 10-29 lines, ignoring generated files. and removed size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. labels Jan 13, 2022
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sre-bot commented Jan 13, 2022 •
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Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/c4fedb99a8f3d3175117aded85078d08979db892

@LittleFall LittleFall changed the title copr: Fix the crash when mpp balancer receive empty task list. mpp: Fix the crash and report when mpp generate empty task list. Jan 13, 2022
@LittleFall LittleFall changed the title mpp: Fix the crash and report when mpp generate empty task list. mpp: Fix the crash or error when mpp generate empty task list. Jan 13, 2022
@ti-chi-bot ti-chi-bot added release-note Denotes a PR that will be considered when it comes time to generate release notes. and removed release-note-none Denotes a PR that doesn't merit a release note. do-not-merge/needs-linked-issue labels Jan 13, 2022
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Could you add some explanations about in what scenarios will the number of mpp tasks be 0, and why it is only a warning instead of error.

fuzhe1989
fuzhe1989 reviewed Jan 14, 2022
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planner/core/fragment.go Outdated Show resolved Hide resolved
planner/core/fragment.go
childrenTasks = childrenTasks[0:1]
if len(childrenTasks) > 0 {
childrenTasks = childrenTasks[0:1]
}
}
tasks = e.constructMPPTasksByChildrenTasks(childrenTasks)
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early return in constructMPPTasksByChildrenTasks or at here when childrenTasks is empty?

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Yes, but it seems unnecessary to add these special judgment logics for rare cases?

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Why not check the range and for empty range, do not construct mpp task at all?

@ti-chi-bot ti-chi-bot added size/M Denotes a PR that changes 30-99 lines, ignoring generated files. and removed size/S Denotes a PR that changes 10-29 lines, ignoring generated files. labels Jan 14, 2022
@LittleFall
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Why not check the range and for empty range, do not construct mpp task at all?

Maintain logic consistency with batch cop requests(func sendBatch), maybe we can refactor these logic at master version instead of this bugfix.

@ti-chi-bot ti-chi-bot added the status/can-merge Indicates a PR has been approved by a committer. label Jan 14, 2022
@ti-chi-bot ti-chi-bot merged commit f1f9230 into pingcap:master Jan 14, 2022
@LittleFall LittleFall deleted the bugfix/31636 branch January 14, 2022 07:26
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/run-cherry-picker

@LittleFall LittleFall added needs-cherry-pick-release-5.2 needs-cherry-pick-release-5.3 Type: Need cherry pick to release-5.3 needs-cherry-pick-release-5.4 Should cherry pick this PR to release-5.4 branch. labels Jan 14, 2022
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/run-cherry-picker

ti-srebot pushed a commit to ti-srebot/tidb that referenced this pull request Jan 14, 2022
@LittleFall @ti-srebot
cherry pick pingcap#31658 to release-5.3
d5f4208 
Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
@ti-srebot ti-srebot mentioned this pull request Jan 14, 2022
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cherry pick to release-5.3 in PR #31695

ti-srebot pushed a commit to ti-srebot/tidb that referenced this pull request Jan 14, 2022
@LittleFall @ti-srebot
cherry pick pingcap#31658 to release-5.2
8b0d754 
Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
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cherry pick to release-5.2 in PR #31696

ti-srebot pushed a commit to ti-srebot/tidb that referenced this pull request Jan 14, 2022
@LittleFall @ti-srebot
cherry pick pingcap#31658 to release-5.4
d2d729a 
Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
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cherry pick to release-5.4 in PR #31697

ti-chi-bot pushed a commit that referenced this pull request Jan 14, 2022
@ti-srebot
mpp: Fix the crash or error when mpp generate empty task list. (#31658)…
ed1cd2a 
… (#31697)

close #31636
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ichn-hu commented Feb 14, 2022

/run-cherry-picker

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ti-srebot pushed a commit to ti-srebot/tidb that referenced this pull request Feb 14, 2022
@LittleFall @ti-srebot
cherry pick pingcap#31658 to release-5.1
01c3f96 
Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
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cherry pick to release-5.1 in PR #32316

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ichn-hu commented Feb 14, 2022

/run-cherry-pick

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ichn-hu commented Feb 14, 2022

/run-cherry-pick

ti-chi-bot pushed a commit that referenced this pull request Feb 22, 2022
@ti-srebot
mpp: Fix the crash or error when mpp generate empty task list. (#31658)…
d139c62 
… (#31695)

close #31636
@LittleFall LittleFall mentioned this pull request Mar 14, 2022
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ti-chi-bot pushed a commit that referenced this pull request Apr 14, 2022
@ti-srebot
mpp: Fix the crash or error when mpp generate empty task list. (#31658)…
58d1bd9 
… (#31696)

close #31636
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@fuzhe1989 fuzhe1989 fuzhe1989 left review comments

@hanfei1991 hanfei1991 hanfei1991 approved these changes

@windtalker windtalker windtalker approved these changes

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TiDB crash for the error of cannot find mpp task
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