Bug #84288 index limits incorrect and out of date
Submitted: 20 Dec 2016 21:07 Modified: 4 Jan 2017 20:43
Reporter: Rick James Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server: Documentation Severity:S3 (Non-critical)
Version:5.7, 8.0 OS:Any
Assigned to: CPU Architecture:Any
Tags: documentation, indexes, limits

[20 Dec 2016 21:07] Rick James 
Description:
http://dev.mysql.com/doc/refman/5.7/en/features.html  says

"The maximum index width is 767 bytes for InnoDB tables, or 1000 for MyISAM."

* The 767 refers to a single column, not the entire index.  (Hence, the statement is wrong, or at least ambiguous, in older versions.
* 5.6 can override the 767.
* 5.7 default exceeds the 767.
* 8.0 gets rid of MyISAM.

This bug arises from a forum entry: 
http://dba.stackexchange.com/questions/158115/maximum-number-of-columns-in-primary-key

How to repeat:
N/A

Suggested fix:
Revise the entire sentence.  Have a different sentence for each version.  Optionally, throw out the sentence.
[21 Dec 2016 4:19] MySQL Verification Team 
Hello Rick James,

Thank you for the report and feedback!

Thanks,
Umesh
[4 Jan 2017 13:58] Daniel Price 
Posted by developer:
 
The referenced documentation was updated. 

Thank you for the bug report.