text: CREATE TABLE releases (
      version         FLOAT         PRIMARY KEY
                      COMMENT 'Version of the Sqitch registry.',
      installed_at    TIMESTAMP     NOT NULL
                      COMMENT 'Date the registry release was installed.',
      installer_name  VARCHAR(255)  NOT NULL
                      COMMENT 'Name of the user who installed the registry release.',
      installer_email VARCHAR(255)  NOT NULL
                      COMMENT 'Email address of the user who installed the registry release.'
  ) ENGINE  InnoDB,
    CHARACTER SET 'utf8',
    COMMENT 'Sqitch registry releases.'
  ;
  
  -- Add the script_hash column to the changes table. Copy change_id for now.
  ALTER TABLE changes ADD COLUMN script_hash VARCHAR(40) NULL UNIQUE AFTER change_id;
  UPDATE changes SET script_hash = change_id;
  
  -- Allow "merge" events.
  ALTER TABLE events CHANGE event event ENUM ('deploy', 'fail', 'merge', 'revert') NOT NULL;
  