time: fix the fraction loss when encountering time string with timezone suffix (#37820)

[ti-srebot]

cherry-pick #37820 to release-5.1
You can switch your code base to this Pull Request by using git-extras:

# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/37991

After apply modifications, you can push your change to this PR via:

git push [email protected]:ti-srebot/tidb.git pr/37991:release-5.1-b8d929c3c754

---

What problem does this PR solve?

Issue Number: close #35291

Problem Summary:

What is changed and how it works?

Identify the position of the timezone before identifying the position of the fraction in the time string to avoid the accuracy loss. Timezone will also be checked later to ensure compatibility so that there is duplicate detection for timezone.

Check List

Tests

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

DROP TABLE IF EXISTS `testSetObjectTime`;
CREATE TABLE `testSetObjectTime` (
  `id` int(11) DEFAULT NULL,
  `d` time(6) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;
INSERT INTO testSetObjectTime VALUES (1, '2020-01-01 12:00:00.123456000+05:00');
INSERT INTO testSetObjectTime VALUES (2, '2020-01-01 12:00:00.123456+05:00');
SELECT * FROM testSetObjectTime;

+------+-----------------+
| id   | d               |
+------+-----------------+
|    1 | 15:00:00.123456 |
|    2 | 15:00:00.123456 |
+------+-----------------+

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

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has not been approved.

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[ti-srebot]

/run-all-tests

[ti-chi-bot]

@ti-srebot: This cherry pick PR is for a release branch and has not yet been approved by release team.
Adding the do-not-merge/cherry-pick-not-approved label.

To merge this cherry pick, it must first be approved by the collaborators.

AFTER it has been approved by collaborators, please ping the release team in a comment to request a cherry pick review.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[Qiaolin-Yu]

/merge

[ti-chi-bot]

@Qiaolin-Yu: /merge is only allowed for the committers, you can assign this pull request to the committer in list by filling /assign @committer in the comment to help merge this pull request.

In response to this:

/merge

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.