Search like that :
/reports?utf8=✓&search=neverendingquery (Do not try in production)

I had to KILL the query in order to get foreman working again.
The query produced is :

SELECT  DISTINCT `reports`.id FROM `reports` LEFT OUTER JOIN `hosts` ON `hosts`.`id` = `reports`.`host_id` AND `hosts`.`type` IN ('Host::Managed') LEFT OUTER JOIN `hosts` `hosts_reports_join` ON `hosts_reports_join`.`id` = `reports`.`host_id` AND `hosts_reports_join`.`type` IN ('Host::Managed') LEFT OUTER JOIN `environments` ON `environments`.`id` = `hosts_reports_join`.`environment_id` LEFT OUTER JOIN `logs` ON `logs`.`report_id` = `reports`.`id` LEFT OUTER JOIN `messages` ON `messages`.`id` = `logs`.`message_id` LEFT OUTER JOIN `logs` `logs_reports_join` ON `logs_reports_join`.`report_id` = `reports`.`id` LEFT OUTER JOIN `sources` ON `sources`.`id` = `logs_reports_join`.`source_id` WHERE ((`hosts`.`name` LIKE '%neverendingquery%' OR `environments`.`name` LIKE '%neverendingquery%' OR `messages`.`value` LIKE '%neverendingquery%' OR `sources`.`value` LIKE '%neverendingquery%')) ORDER BY `reports`.`reported_at` DESC LIMIT 20 OFFSET 0

mysql-server 5.5 seems to take A LOT of time to answer (more than 30 minutes in production for me).
Gem used : mysql (2.9.1) and mysql2 (0.3.11)

database.yml :
production:
adapter: mysql
database: foreman
host: localhost
port:
username: foreman
password: xxx
encoding: utf8