table: handling the boundary value of the timestamp type's default value

[zimulala]

What problem does this PR solve?

Fix #9513
Before this PR:

tidb> select now();
+---------------------+
| now()               |
+---------------------+
| 2019-02-28 21:09:20 |
+---------------------+
1 row in set (0.00 sec)

tidb> create table t(a int);
Query OK, 0 rows affected (0.01 sec)

tidb>  ALTER TABLE t ADD COLUMN ts timestamp DEFAULT '1970-01-01 08:00:01';
ERROR 1067 (42000): Invalid default value for 'ts'

After this PR, we can successfully execute ALTER TABLE t ADD COLUMN ts timestamp DEFAULT '1970-01-01 08:00:01';.

What is changed and how it works?

Using the correct time zone when checking the default value.

Check List

Tests

• Unit test

Related changes

• Need to cherry-pick to the release branch

[codecov-io]

Codecov Report

Merging #9578 into master will decrease coverage by 0.0191%.
The diff coverage is 70.5882%.

@@               Coverage Diff                @@
##             master      #9578        +/-   ##
================================================
- Coverage   77.5768%   77.5577%   -0.0192%     
================================================
  Files           403        403                
  Lines         81844      81850         +6     
================================================
- Hits          63492      63481        -11     
- Misses        13656      13667        +11     
- Partials       4696       4702         +6

[zimulala]

PTAL @crazycs520 @jackysp @tiancaiamao

[zimulala]

PTAL @crazycs520 @jackysp @tiancaiamao

[crazycs520]

REST LGTM

[zimulala]

PTAL @crazycs520

[crazycs520]

LGTM

[XuHuaiyu]

LGTM

[zimulala]

PTAL @winkyao

[zimulala]

PTAL @winkyao

[zimulala]

PTAL @winkyao

[winkyao]

LGTM

[zz-jason]

/run-all-tests