Bug #96843 MySQL Server failed to restart after set default_collation_for_utf8mb4
Submitted: 12 Sep 2019 3:02 Modified: 12 Sep 2019 8:18
Reporter: Efrey Kong Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL for Windows: Installer Severity:S1 (Critical)
Version:8.0.17.0 OS:Microsoft Windows (10 Enterprise 1803)
Assigned to: CPU Architecture:Any
Tags: default_collation_for_utf8mb4

[12 Sep 2019 3:02] Efrey Kong
Description:
I've installed MySQL 5.5 previously, and recently I've uninstalled MySQL 5.5 and Installed MySQL Community 8.0.17.0 (Custom mode, MySQL server & Workbench selected).

After that, I've enabled default_collation_for_utf8mb4changed for MySQL (via Workbench > Options File > General > International > default_collation_for_utf8mb4), then I've restarted MySQL server service via Services management windows. but MySQL failed to start.

I've checked C:\ProgramData\MySQL\MySQL Server 8.0\Data folder, and there is a error file "EKSTUDIO.err" (My PC's name is EKSTUDIO), and there are some error message in it: "[ERROR] [MY-000067] [Server] unknown variable 'default_collation_for_utf8mb4=utf8mb4_0900_ai_ci'."

Temporary fix:
Open my.ini file, find and remove `default_collation_for_utf8mb4=utf8mb4_0900_ai_ci`, and then save the file.
restart MySQL service successfully.

How to repeat:
This issue has also been repeated on another my computer. Here is the step to reproduce:

1. Open MySQL Workbench (8.0.17)
2. Swicth to `Administration` tab, and click `Options File`
3. Scroll down to the International group, check on the `default_collation_for_utf8mb4` option, keep the default value `utf8mb4_0900_ai_ci`. then click `Apply...` button to take effective.

4. Open Windows Services management windows, go to MySQL service, and choose to restart. then an error message will be popped up.
[12 Sep 2019 8:18] Umesh Shastry
Hello Efrey Kong,

Thank you for the report and feedback.
Observed this on Win10 with installer 1.4.31.

regards,
Umesh