Fix unstable drop table unit test

[lidezhu]

What problem does this PR solve?

Issue Number: close #5060

Problem Summary: To make the segments in the unit test split more easily, we change the dt related params in settings.
But we just change the settings in the local context, and in the global context the settings is unchanged.
When processing write request, DeltaMergeStore calls checkSegment with the local context we passed. So it splits as we expected.
But we do several DeltaMergeStore initialization in the test, and in the initialization process, DeltaMergeStore calls checkSegment with the global_context, and try to merge the segments which make the test not stable

What is changed and how it works?

Make the settings in local context and global_context consistent.

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
• Lloyd-Pottiger

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[lidezhu]

/run-all-tests

[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/tests/gtest_dm_storage_delta_merge.cpp        1773               351    80.20%          18                 0   100.00%         741                12    98.38%         564               267    52.66%
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                                                                                                                 1773               351    80.20%          18                 0   100.00%         741                12    98.38%         564               267    52.66%

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
18282      9734             46.76%    204990  97609        52.38%

full coverage report (for internal network access only)

[JaySon-Huang]

LGTM with small comment

[lidezhu]

/merge

[ti-chi-bot]

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

/run-all-tests

You only need to trigger /merge once, and if the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

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[ti-chi-bot]

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

Commit hash: b745aa2

[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/tests/gtest_dm_storage_delta_merge.cpp        1773               351    80.20%          18                 0   100.00%         740                12    98.38%         564               267    52.66%
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                                                                                                                 1773               351    80.20%          18                 0   100.00%         740                12    98.38%         564               267    52.66%

Coverage summary

Functions  MissedFunctions  Executed  Lines   MissedLines  Cover
18282      9732             46.77%    205087  97594        52.41%

full coverage report (for internal network access only)

[ti-chi-bot]

In response to a cherrypick label: new pull request created: #5072.