ttl: fix a wrong ttl's job schedule for TTL table upgraded from 6.5 (#56540)

[ti-chi-bot]

This is an automated cherry-pick of #56540

What problem does this PR solve?

Issue Number: close #56539

Problem Summary:

In 6.5, the TTL table is created without meta ttl_job_interval, so after upgraded, the SCHED_POLICY_EXPR in mysql.tidb_timers is also empty that causing the frequent scheduling of TTL job.

What changed and how does it work?

When syncing the timer, insert a default value if ttl_job_interval is empty

Check List

Tests

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

  • I checked and no code files have been changed.

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

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[codecov]

Codecov Report

Attention: Patch coverage is 93.33333% with 1 line in your changes missing coverage. Please review.

Please upload report for BASE (release-7.5@74983c9). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-7.5     #56593   +/-   ##
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  Coverage               ?   72.1150%           
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  Files                  ?       1415           
  Lines                  ?     413004           
  Branches               ?          0           
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  Hits                   ?     297838           
  Misses                 ?      95267           
  Partials               ?      19899           

Flag	Coverage Δ
unit	72.1150% <93.3333%> (?)

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Components	Coverage Δ
dumpling	52.9400% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	53.5564% <0.0000%> (?)

[YangKeao]

LGTM

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-10-14 06:44:55.66894443 +0000 UTC m=+253492.817854255: ☑️ agreed by lcwangchao.
• 2024-10-14 08:28:31.281422641 +0000 UTC m=+259708.430332457: ☑️ agreed by YangKeao.

[bb7133]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bb7133, lcwangchao, YangKeao

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