Tidb: mysql client 8.0 failed to connect to tidb-server

[lysu]

1. What did you do?
   If possible, provide a recipe for reproducing the error.

use mysql 8.0 client.

➜ ./bin/mysql -h 127.0.0.1 -P 4000 -u root
ERROR 1105 (HY000): Unknown charset id 255

➜ ./bin/mysql -V
./bin/mysql  Ver 8.0.11 for osx10.13 on x86_64 (Source distribution)

1. What did you expect to see?

connected

1. What did you see instead?

ERROR 1105 (HY000): Unknown charset id 255

1. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

Release Version: v2.1.0-alpha-89-g0547af60a
Git Commit Hash: 0547af60af60d16e262208ca0684e771386f62eb
Git Branch: dev-fix-maria-db-client
UTC Build Time: 2018-06-28 03:21:07
GoVersion: go version go1.10.1 linux/amd64
Race Enabled: false
TiKV Min Version: 2.1.0-alpha.1-ff3dd160846b7d1aed9079c389fc188f7f5ea13e

This issue is related with 8.0 new collation.

before we fix it, the user can add --default-character-set utf8when use MySQL 8.0 client to bypass this problem.

[breeswish]

hint: it should be --default-character-set in mysql Ver 8.0.11.

[lysu]

IMHO, current the handling logic of TiDB is more right than MySQL does, and we should not change this logic in current stage.

In MySQL, use client-5.7 will forward compatible with server-8.0 like this. it will slient make collation be the global_system_variables's values, and user know nothing about this, they will still think everything is well but use collation which they doesn't wanted, I think it's very dangerous.

So, we should NOT forward compatible with 8.0's new utf8mb4_0900_ai_ci and keep return error to make user know collaction question until we support unicode9.0 in TiDB.

When meet this error, we can

1. add --default-character-set utf8 to mysql-client 8.0's arguments
2. modify /etc/mysql/mysql.cnf or /etc/mysql/conf.d/mysql.conf set mysql.default-character-set=utf8

and we will support unicode 9.0 in future.

[fkpwolf]

For MySql Workbench 8.0, there is no way to change character-set. Have to switch to Sequel Pro.