didn't output good width for timestamp column sometimes

[lance6716]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

in mysql client

set @@explicit_defaults_for_timestamp = 1;
create table t(c timestamp);
insert into t values (null);
select * from t;

2. What did you expect to see? (Required)

mysql> select * from t;
+------+
| c    |
+------+
| NULL |
+------+
1 row in set (0.00 sec)

3. What did you see instead (Required)

mysql> select * from t;
+---+
| c |
+---+
| NULL |
+---+
1 row in set (0.00 sec)

4. What is your TiDB version? (Required)

Release Version: v4.0.0-beta.2-1552-ga81c89f89
Edition: Community
Git Commit Hash: a81c89f89b6fbc81c23f1bd341b3bc6c0cb4475f
Git Branch: HEAD
UTC Build Time: 2020-11-12 20:00:53
GoVersion: go1.13.4
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[ichn-hu]

This is an interesting bug, after investigation, it might be that TiDB wrongly calculated the Flag column information, and a simplest reproduce is to

╰─$ mysql -u root -p -h 0.0.0.0 -P 4000 -D test --column-type-info                                                         
mysql> select NULL as a;
Field   1:  `a`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       NULL
Collation:  binary (63)
Length:     0
Max_length: 0
Decimals:   0
Flags:      NOT_NULL BINARY NUM


+---+
| a |
+---+
| NULL |
+---+
1 row in set (0.00 sec)

While in mysql

mysql>  select NULL as a;
Field   1:  `a`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       NULL
Collation:  binary (63)
Length:     0
Max_length: 0
Decimals:   0
Flags:      BINARY NUM


+------+
| a    |
+------+
| NULL |
+------+
1 row in set (0.00 sec)

[xuyifangreeneyes]

/assign

[xuyifangreeneyes]

#19029 can fix this issue.

[lance6716]

fixed somehow

MySQL [(none)]>  select NULL as a;
Field   1:  `a`
Org_field:  `a`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       NULL
Collation:  binary (63)
Length:     0
Max_length: 0
Decimals:   0
Flags:      BINARY NUM 


+------+
| a    |
+------+
| NULL |
+------+
1 row in set (0.001 sec)

MySQL [(none)]> select tidb_version();
Field   1:  `tidb_version()`
Org_field:  `tidb_version()`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       VAR_STRING
Collation:  utf8mb3_bin (83)
Length:     1136
Max_length: 284
Decimals:   31
Flags:      NOT_NULL 


+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                               |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v6.5.0
Edition: Community
Git Commit Hash: 706c3fa3c526cdba5b3e9f066b1a568fb96c56e3
Git Branch: heads/refs/tags/v6.5.0
UTC Build Time: 2022-12-27 03:50:44
GoVersion: go1.19.3
Race Enabled: false
TiKV Min Version: 6.2.0-alpha
Check Table Before Drop: false
Store: tikv |
+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.001 sec)