executor, infoschema: SHOW COLLATIONS shows supported collations only

[bb7133]

What problem does this PR solve?

This PR aims to fix 2 compatibility issues:

• In TIDB, the SHOW CHARSET command shows only supported charsets:

mysql> show charset;
+---------+---------------+-------------------+--------+
| Charset | Description   | Default collation | Maxlen |
+---------+---------------+-------------------+--------+
| utf8    | UTF-8 Unicode | utf8_bin          |      3 |
| utf8mb4 | UTF-8 Unicode | utf8mb4_bin       |      4 |
| ascii   | US ASCII      | ascii_bin         |      1 |
| latin1  | Latin1        | latin1_bin        |      1 |
| binary  | binary        | binary            |      1 |
+---------+---------------+-------------------+--------+

But SHOW COLLATIONS shows all collations that supported in MySQL 5.7:

mysql> show collation;
+--------------------------+----------+------+---------+----------+---------+
| Collation                | Charset  | Id   | Default | Compiled | Sortlen |
+--------------------------+----------+------+---------+----------+---------+
| big5_chinese_ci          | big5     |    1 | Yes     | Yes      |       1 |
| latin2_czech_cs          | latin2   |    2 |         | Yes      |       1 |
| dec8_swedish_ci          | dec8     |    3 | Yes     | Yes      |       1 |
| cp850_general_ci         | cp850    |    4 | Yes     | Yes      |       1 |
| latin1_german1_ci        | latin1   |    5 |         | Yes      |       1 |
| hp8_english_ci           | hp8      |    6 | Yes     | Yes      |       1 |
| koi8r_general_ci         | koi8r    |    7 | Yes     | Yes      |       1 |
| latin1_swedish_ci        | latin1   |    8 | Yes     | Yes      |       1 |
| latin2_general_ci        | latin2   |    9 | Yes     | Yes      |       1 |
...
| utf8mb4_german2_ci       | utf8mb4  |  244 |         | Yes      |       1 |
| utf8mb4_croatian_ci      | utf8mb4  |  245 |         | Yes      |       1 |
| utf8mb4_unicode_520_ci   | utf8mb4  |  246 |         | Yes      |       1 |
| utf8mb4_vietnamese_ci    | utf8mb4  |  247 |         | Yes      |       1 |
+--------------------------+----------+------+---------+----------+---------+
219 rows in set (0.01 sec)

It's better for SHOW COLLATIONS to display only supported collations.

• The Default column is wrong for some of SHOW COLLATION results:

mysql> show collation where Collation='utf8_bin';
+-----------+---------+------+---------+----------+---------+
| Collation | Charset | Id   | Default | Compiled | Sortlen |
+-----------+---------+------+---------+----------+---------+
| utf8_bin  | utf8    |   83 |         | Yes      |       1 |
+-----------+---------+------+---------+----------+---------+
1 row in set (0.00 sec)

The default collation of utf8 in TiDB is utf8_bin

What is changed and how it works?

This main change is from parser PR: pingcap/parser#295

Check List

Tests

• Integration test

Code changes

• Has interface methods change

Side effects

• Breaking backward compatibility in some SHOW result

Related changes

• Need to cherry-pick to the release branch

[morgo]

Thank you for working on this. I think it's a great enhancement!

[crazycs520]

can we remove this function in parser now?

[bb7133]

It looks reasonable, I will try to remove it in another PR, thanks

[tiancaiamao]

LGTM

[zz-jason]

@bb7133 Please merge master && resolve conflicts. BTW please add some proper labels for this PR.

[winkyao]

LGTM, please fix ci

[tiancaiamao]

The circle CI fail is misleading, it actually pass all tests
I remove the redundant 'parser replace check'
#10228

[codecov]

Codecov Report

Merging #10186 into master will increase coverage by 0.0076%.
The diff coverage is 66.6666%.

@@               Coverage Diff               @@
##            master     #10186        +/-   ##
===============================================
+ Coverage   77.949%   77.9566%   +0.0076%     
===============================================
  Files          407        407                
  Lines        83543      82601       -942     
===============================================
- Hits         65121      64393       -728     
+ Misses       13591      13431       -160     
+ Partials      4831       4777        -54

[bb7133]

/run-all-tests

[bb7133]

PTAL @crazycs520 @zz-jason