ERROR 1071 (42000) at line 323: Specified key was too long; max key length is 1000 bytes

Al intentar importar un volcado de mambo/joomla mysql en utf8 se obtiene este error:

ERROR 1071 (42000) at line 323: Specified key was too long; max key length is 1000 bytes

La solucion es o bien usar la base de datos con codificacion latin1 o realizar esta modificacion:

UNIQUE KEY `section_value_value_aro` (`section_value`,`value`),
UNIQUE KEY `mos_gacl_section_value_value_aro` (`section_value`,`value`),

por esto :

UNIQUE KEY `section_value_value_aro` (`section_value` (90),`value`),
UNIQUE KEY `mos_gacl_section_value_value_aro` (`section_value` (90),`value`),

El resultado final sería:

CREATE TABLE `mos_core_acl_aro` (
`aro_id` int(11) NOT NULL auto_increment,
`section_value` varchar(240) NOT NULL default '0',
`value` varchar(240) NOT NULL default '',
`order_value` int(11) NOT NULL default '0',
`name` varchar(255) NOT NULL default '',
`hidden` int(11) NOT NULL default '0',
PRIMARY KEY (`aro_id`),
UNIQUE KEY `section_value_value_aro` (`section_value` (90),`value`),
UNIQUE KEY `mos_gacl_section_value_value_aro` (`section_value` (90),`value`),
KEY `hidden_aro` (`hidden`),
KEY `mos_gacl_hidden_aro` (`hidden`)
) TYPE=MyISAM

Más información en: http://mysql.org/doc/refman/5.1/en/multiple-column-indexes.html

y http://dev.mysql.com/doc/mysql/en/CREATE_INDEX.html