text: --
  -- Holds acknowledgedments information.
  --
  CREATE TABLE acknowledgements (
    acknowledgement_id int NOT NULL auto_increment,
    entry_time int NOT NULL,
    host_id int NOT NULL,
    service_id int default NULL,
  
    author varchar(64) default NULL,
    comment_data varchar(255) default NULL,
    deletion_time int default NULL,
    instance_id int default NULL,
    notify_contacts boolean default NULL,
    persistent_comment boolean default NULL,
    state smallint default NULL,
    sticky boolean default NULL,
    type smallint default NULL,
  
    PRIMARY KEY (acknowledgement_id),
    INDEX (host_id),
    INDEX (instance_id),
    INDEX (entry_time),
    UNIQUE (entry_time, host_id, service_id),
    FOREIGN KEY (host_id) REFERENCES hosts (host_id)
      ON DELETE CASCADE,
    FOREIGN KEY (instance_id) REFERENCES instances (instance_id)
      ON DELETE SET NULL
  ) ENGINE=InnoDB;
  