Host column size still too big for utf8 character set

[jhindersson]

The commit f8becb3 changed the host column size from 1024 to 512, when using default-character-set utf8 this is still too big and needs to be max 255.

This prevents upgrading to the latest stable released version (3.1.2 20180523).

[mandeepdhami]

Why is this too big?

[jhindersson]

As utf8 charset is 3 bytes per characters a 512 character size index would be 1536 bytes which is larger than the max of 767 bytes (255*3 = 765 though which is 2 bytes within margin). Actually following MySQL best practices it should use utf8mb4 which is 4 bytes per character which would limit the field further to 191 characters.

The error produced is the following:
DBError: (pymysql.err.InternalError) (1071, u'Specified key was too long; max key length is 767 bytes') [SQL: u'CREATE INDEX ix_aim_endpoint_group_static_paths_host ON aim_endpoint_group_static_paths (host)']", "stdout": "", "stdout_lines": [], "warnings": []}

Actually the value is raised in MySQL 5.7 or MariaDB 10.2 but both includes new features which breaks alembic in it's current version (0.8.10) so this might be raised but not before the builds is done using alembic version 0.9.8.