There are a few confluence tables (we use MySQL) whose character set is set to utf8 in their create table statement - and collation is not set. For such tables, mysql sets the character set as utf8_general_ci, that is the default for utf8. This will be the case even if the character set/collation is set at the database level as utf8/utf8-bin.
When we upgraded from 3.5 to 4.3.7, the upgrade took almost 20 hrs - this was due to the collation mismatch between 'content' and 'cwd_user'. Once the collation of that joining column in 'content' was changed to utf8-bin, the upgrade finished in 1 hr.
I have attachments, attachmentdata, content,bodycontent, spaces and spacepermissions whose collation is utf8_general_ci - and want to change to utf8-bin. I hope the change will improve wiki performance.
Are there any known issues with this change ?