Fix data race of DeltaIndexManager. (#4459)

[ti-chi-bot]

This is an automated cherry-pick of #4459

What problem does this PR solve?

Issue Number: close #4405

Problem Summary: current_size may be read and written concurrently.

What is changed and how it works?

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

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

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• JaySon-Huang
• lidezhu

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[JaySon-Huang]

lgtm

[JinheLin]

/merge

[ti-chi-bot]

@JinheLin: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 9d8b49c

[sre-bot]

Coverage for changed files

Filename                                                                                                          Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
/home/jenkins/agent/workspace/tiflash-build-common/tiflash/dbms/src/Storages/DeltaMerge/DeltaIndexManager.cpp          46                 6    86.96%           4                 0   100.00%          83                 8    90.36%          28                11    60.71%
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                                                                                                  46                 6    86.96%           4                 0   100.00%          83                 8    90.36%          28                11    60.71%

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
16980      9544             43.79%    191342  96884        49.37%

full coverage report (for internal network access only)