Bug #103336 MySQL - Blackhole max index key length < InnoDB
Submitted: 15 Apr 2021 18:22 Modified: 16 Apr 2021 7:39
Reporter: Adam Cable (OCA) Email Updates:
Status: Duplicate Impact on me:
None 
Category:MySQL Server: DDL Severity:S3 (Non-critical)
Version: OS:Any
Assigned to: CPU Architecture:Any

[15 Apr 2021 18:22] Adam Cable 
Description:
Currently the maximum index key length for an InnoDB table is 3072 bytes.
We typically use the Blackhole storage engine on various replicas with low storage space, or other requirements.
The expectation is there that you should be able to run an ALTER TABLE ... ENGINE=BLACKHOLE; command without issues on any InnoDB table.
However, if the index length is > 1000 bytes this fails.
This PR aligns the maximum key length with the InnoDB storage engine.

How to repeat:
Create a table with index > 1000 bytes on InnoDB and run ALTER TABLE ... ENGINE=BLACKHOLE;

Suggested fix:
https://github.com/mysql/mysql-server/pull/335
[16 Apr 2021 7:39] MySQL Verification Team 
Hello Adam Cable,

Thank you for the report and feedback.
Imho this is duplicate of Bug #53588, please see Bug #53588

regards,
Umesh