types: fix the bug about the wrong query result for decimal type (#22507)

[ti-srebot]

cherry-pick #22507 to release-4.0
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# In tidb repo:
git pr https://github.com/pingcap/tidb/pull/23196

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---

What problem does this PR solve?

Issue Number: close #22496

Problem Summary:

MySQL [test]> create table t12(d decimal(15,2));
MySQL [test]> insert into t12 values('1,999.00');
MySQL [test]> select * from t12;
+------+
| d |
+------+
| 1.00 |
+------+
1 row in set (0.00 sec)

The select about decimal type show the wrong result.

What is changed and how it works?

What's Changed:
update the FromString function for MyDecimal for the situation like "1,999.00" and "1,999,999.00"

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Unit test
• Manual test (add detailed scripts or steps below)

Release note

• types: fix the bug about the wrong query result for decimal type

[ti-srebot]

/run-all-tests

[ti-srebot]

@jyz0309 you're already a collaborator in bot's repo.

[jyz0309]

@lysu @XuHuaiyu cherry-pick,PTAL

[XuHuaiyu]

/lgtm

[lysu]

/lgtm

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• XuHuaiyu
• lysu

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[zhouqiang-cl]

/merge

[ti-chi-bot]

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

Commit hash: 69b502d

[ti-chi-bot]

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[zhouqiang-cl]

/merge