I'm having trouble installing Wikibase according to the instructions at https://www.mediawiki.org/wiki/Wikibase/Installation. The problem occurs during this step:
The failure appears to be a consequence of T99459. Here's the merge link:
Apparently, upping the size to 310 characters (in Unicode) results in keys that are larger than the 767 byte limit in MySQL. The update.php script now fails with this error:
Error: 1071 Specified key was too long; max key length is 767 bytes (127.0.0.1:3306)
If I manually hack the sizes back to 255 and try again, the install process appears to be successful.
I was able to reproduce the problem when deploying on both Linux and MacOS.
Note that I am trying to set up a project that is powered by Wikibase along the lines of http://www.eagle-network.eu/wiki/index.php/Main_Page rather than work with the Wikidata instance.