CREATE TABLE session_role (
Session_sessionId bigint(20) NOT NULL,
activeRoles_roleId varchar(255) NOT NULL,
PRIMARY KEY(Session_sessionId,activeRoles_roleId),
UNIQUE KEY activeAccounts_actorId (activeRoles_roleId),
KEY `FK38CC06CCF5B03D50` (Session_sessionId),
KEY `FK38CC06CC4085AE4` (activeRoles_roleId),
CONSTRAINT `FK38CC06CC4085AE4` FOREIGN KEY (activeRoles_roleId)
REFERENCES role(roleId),
CONSTRAINT `FK38CC06CCF5B03D50` FOREIGN KEY (Session_sessionId)
REFERENCES session (sessionId)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

This is four indexes for a two-column table! Of course nobody has actually written this, this is generated by JBoss/Hibernate, with a MySQL database used for storing data. Be very careful with code generators....