MySQL Bugs: #86379: Cannot create new Unique Index

Bug #86379	Cannot create new Unique Index
Submitted:	18 May 2017 23:56	Modified:	4 Aug 2017 0:08
Reporter:	Knight Yoshi	Email Updates:
Status:	Can't repeat	Impact on me:	None
Category:	MySQL Workbench	Severity:	S3 (Non-critical)
Version:	6.3.9	OS:	MacOS (macOS 10.12.x Sierra x86_64)
Assigned to:		CPU Architecture:	Any
Tags:	WBBugReporter

Description:
When trying to add a unique index to a new field in an existing table MySQL Workbench throws an error saying it already exists. This happens when I use both the interface for adding fields/indexes and when I try to manually execute the SQL statement.

How to repeat:
Open a connection to a DB
In the left pane click the icon to edit a table via the UI
Add a new field and set it to be UNIQUE
Click Apply

This may actually be a MySQL error, not a WB error. I just tried executing the same SQL statement in phpMyAdmin and got a duplicate entry error.

I checked the INNODB_SYS_INDEXES table and no results were returned with the index I'm trying to create.

Thank you for the bug report. Then what is the sql statement?. Thanks.

No feedback was provided for this bug for over a month, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".

I didn't see the reply to this.

SQL Statement:
ALTER TABLE `gaiatools_yii`.`user` 
ADD UNIQUE INDEX `userslug_UNIQUE` (`userslug` ASC)

Error 1062: Duplicate entry '' for key 'userslug_UNIQUE'
SQL Statement:
ALTER TABLE `gaiatools_yii`.`user` 
ADD UNIQUE INDEX `userslug_UNIQUE` (`userslug` ASC)

Ultimately I had to drop and recreate the table to add the UNIQUE index.

I wasn't able to repeat with WB 5.3.9 on MAC OS 10;12;6 against local server 5.7.18.