types: fix converting decimal to datetime and timestamp

[Debiancc]

What problem does this PR solve?

fix #9770

What is changed and how it works?

In Datum.convertToMysqlTime function add KindMysqlDecimal switch case, and convert decimal to string then parse to Time

Check List

Tests

• Unit Test
• Manual test (Converting decimal to datetime or timestamp when insert is not compatible with MySQL #9770)

mysql> INSERT INTO t1 VALUES (20010101100000.1234566);
Query OK, 1 row affected (0.00 sec)

mysql> select * from t1;
+----------------------------+
| a                          |
+----------------------------+
| 2001-01-01 10:00:00.123456 |
| 2001-01-01 10:00:00.123457 |
| 2001-01-01 10:00:00.123457 |
+----------------------------+
3 rows in set (0.00 sec)

mysql> select tidb_version();
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                                                                             |
| Release Version: v3.0.0-beta-251-gb4cc3e489-dirty
Git Commit Hash: b4cc3e48934afaefbf6d5f65b5414b8b65117234
Git Branch: master
UTC Build Time: 2019-03-26 07:10:09
GoVersion: go version go1.12.1 darwin/amd64
Race Enabled: false
TiKV Min Version: 2.1.0-alpha.1-ff3dd160846b7d1aed9079c389fc188f7f5ea13e
Check Table Before Drop: false |

1 row in set (0.00 sec)

Side effects

• Possible performance regression

[CLAassistant]

All committers have signed the CLA.

[codecov]

Codecov Report

Merging #9899 into master will increase coverage by 0.0757%.
The diff coverage is 100%.

@@               Coverage Diff                @@
##             master      #9899        +/-   ##
================================================
+ Coverage   77.4516%   77.5273%   +0.0757%     
================================================
  Files           404        404                
  Lines         81722      81726         +4     
================================================
+ Hits          63295      63360        +65     
+ Misses        13703      13660        -43     
+ Partials       4724       4706        -18

[qw4990]

Thanks for your contribution.
Could you please add some unit tests in types/datum_test.go and expression/integration_test.go.

[qw4990]

CREATE TABLE t2(a TIMESTAMP);
INSERT INTO t2 VALUES (20010101100000.1234567);

And besides MysqlTime, when TiDB converts a Decimal to Timestamp, it will generate a similar error like ERROR 1105 (HY000): cannot convert datum from decimal to type timestamp..

This problem should have the same reason with MysqlTime.
Could you please fix this problem 😺

[Debiancc]

CREATE TABLE t2(a TIMESTAMP);
INSERT INTO t2 VALUES (20010101100000.1234567);

And besides MysqlTime, when TiDB converts a Decimal to Timestamp, it will generate a similar error like ERROR 1105 (HY000): cannot convert datum from decimal to type timestamp..

This problem should have the same reason with MysqlTime.
Could you please fix this problem 😺

Sure, i will fix that and cover test later.

[qw4990]

/rebuild

[qw4990]

LGTM

[qw4990]

/rebuild

[qw4990]

@Debiancc There are some CI problems, but it seems that they are not caused by this PR.
Could you please resolve these conflicts and rebase this PR to the latest Master branch.

[qw4990]

/rebuild

[alivxxx]

LGTM

[zz-jason]

LGTM

[zz-jason]

/run-all-tests

[zz-jason]

/run-unit-test

[zz-jason]

@Debiancc please cherry pick this change to release 2.1