zabbix监控系统，清除后台的history

zabbix 3.4版本采用如下方法进行

-- alerts table rebuild.
-- ----------------------------
-- Table structure for alerts
-- ----------------------------
SET FOREIGN_KEY_CHECKS=0;
DROP TABLE IF EXISTS `alerts`;
CREATE TABLE `alerts` (
  `alertid` bigint(20) unsigned NOT NULL,
  `actionid` bigint(20) unsigned NOT NULL,
  `eventid` bigint(20) unsigned NOT NULL,
  `userid` bigint(20) unsigned DEFAULT NULL,
  `clock` int(11) NOT NULL DEFAULT '0',
  `mediatypeid` bigint(20) unsigned DEFAULT NULL,
  `sendto` varchar(100) COLLATE utf8_bin NOT NULL DEFAULT '',
  `subject` varchar(255) COLLATE utf8_bin NOT NULL DEFAULT '',
  `message` text COLLATE utf8_bin NOT NULL,
  `status` int(11) NOT NULL DEFAULT '0',
  `retries` int(11) NOT NULL DEFAULT '0',
  `error` varchar(2048) COLLATE utf8_bin NOT NULL DEFAULT '',
  `esc_step` int(11) NOT NULL DEFAULT '0',
  `alerttype` int(11) NOT NULL DEFAULT '0',
  `p_eventid` bigint(20) unsigned DEFAULT NULL,
  `acknowledgeid` bigint(20) unsigned DEFAULT NULL,
  PRIMARY KEY (`alertid`),
  KEY `alerts_1` (`actionid`),
  KEY `alerts_2` (`clock`),
  KEY `alerts_3` (`eventid`),
  KEY `alerts_4` (`status`),
  KEY `alerts_5` (`mediatypeid`),
  KEY `alerts_6` (&