MySQL 索引失效问题分析

初步记录，尚未完成，有待完善。

mchdba-rm-huayuan.mysql.rds.aliyuncs.com:3306:pdd_oms 16:39:40> explain select count(*) as aggregate from `t_unship` where `batch_id` in ('380', '381', '382', '383', '384', '385', '386', '387', '388', '389', '390', '391', '392', '393', '394', '395', '396', '397', '398', '399', '400', '401', '402', '403', '404', '405', '406', '407', '408', '409', '410', '411', '412', '413', '414', '415', '416', '417', '418', '419', '420', '421', '422', '423', '424', '425', '426', '427', '428', '429', '430', '431', '432', '433', '434', '435', '436', '437', '438', '439', '440', '441') and `mall_id` = '23200' and `oprate_status` = '2' and `is_deleted` = '0';+----+-------------+----------+-------+--------------------------+--------------+---------+------+-------+------------------------------------+| id | select_type | table    | type  | possible_keys            | key          | key_len | ref  | rows  | Extra                              |+----+-------------+----------+-------+--------------------------+--------------+---------+------+-------+------------------------------------+|  1 | SIMPLE      | t_unship | range | idx_mall_id,idx_batch_id | idx_batch_id | 8       | NULL | 16182 | Using index condition; Using where |+----+-------------+----------+-------+--------------------------+--------------+---------+------+-------+------------------------------------+1 row in set (0.01 sec)mchdba-rm-huayuan.mysql.rds.aliyuncs.com:3306:pdd_oms 16:39:44> explain select count(1)  as aggregate from `t_unship` force index(idx_mall_id) where `batch_id` in ('380', '381', '382', '383', '384', '385', '386', '387', '388', '389', '390', '391', '392', '393', '394', '395', '396', '397', '398', '399', '400', '401', '402', '403', '404', '405', '406', '407', '408', '409', '410', '411', '412', '413', '414', '415', '416', '417', '418', '419', '420', '421', '422', '423', '424', '425', '426', '427', '428', '429', '430', '431', '432', '433', '434', '435', '436', '437', '438', '439', '440', '441') and `mall_id` = '23200' and `oprate_status` = '2' and `is_deleted` = '0';+----+-------------+----------+------+---------------+-------------+---------+-------+--------+------------------------------------+| id | select_type | table    | type | possible_keys | key         | key_len | ref   | rows   | Extra                              |+----+-------------+----------+------+---------------+-------------+---------+-------+--------+------------------------------------+|  1 | SIMPLE      | t_unship | ref  | idx_mall_id   | idx_mall_id | 8       | const | 167532 | Using index condition; Using where |+----+-------------+----------+------+---------------+-------------+---------+-------+--------+------------------------------------+1 row in set (0.00 sec)mchdba-rm-huayuan.mysql.rds.aliyuncs.com:3306:pdd_oms 16:40:09> CREATE TABLE `t_unship` (  `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT COMMENT '未发货流水id',  `order_sn` varchar(127) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '' COMMENT '关联的订单sn',  `mall_id` bigint(20) unsigned NOT NULL DEFAULT '0' COMMENT '关联的商家id',  `goods_id` bigint(20) unsigned NOT NULL DEFAULT '0' COMMENT '关联的商品id',  `batch_id` bigint(20) unsigned NOT NULL DEFAULT '0' COMMENT '处罚的批次id',  `rule_type` int(3) unsigned NOT NULL DEFAULT '0' COMMENT '处罚规则类型,0:提醒发货,1:超时2天未发货,2:超时4天未发货,3:超时6天未发货',  `sn_type_unique` varchar(63) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '' COMMENT 'order_sn和rule_type生成的唯一组合串',  `check_time` datetime NOT NULL DEFAULT '1970-01-01 08:00:00' COMMENT '确认处罚时间',  `confirm_time` datetime NOT NULL DEFAULT '1970-01-01 08:00:00' COMMENT '订单确认时间',  `promise_ship_time` datetime NOT NULL DEFAULT '1970-01-01 08:00:00' COMMENT '承诺发货时间',  `punish_amount` int(11) unsigned NOT NULL DEFAULT '0' COMMENT '处罚金额',  `oprate_status` int(3) unsigned NOT NULL DEFAULT '0' COMMENT '处罚操作状态,0:未操作,1:忽略,2:已完成',  `is_coupon` int(3) unsigned NOT NULL DEFAULT '0' COMMENT '是否已发优惠券',  `is_custom_sms` int(3) unsigned NOT NULL DEFAULT '0' COMMENT '是否已经给用户发短信',  `is_deleted` int(3) unsigned NOT NULL DEFAULT '0' COMMENT '逻辑删',  `created_at` datetime NOT NULL DEFAULT '1970-01-01 08:00:00' COMMENT '创建时间',  `updated_at` datetime NOT NULL DEFAULT '1970-01-01 08:00:00' COMMENT '修改时间',  `coupon_id` bigint(20) NOT NULL DEFAULT '0' COMMENT '发出的优惠券ID',  `province_id` int(10) unsigned NOT NULL DEFAULT '0',  `province_name` varchar(64) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '',  `city_id` int(10) unsigned NOT NULL DEFAULT '0',  `city_name` varchar(64) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '',  PRIMARY KEY (`id`),  KEY `idx_goods_id` (`goods_id`),  KEY `idx_unique` (`sn_type_unique`),  KEY `t_unship_order_sn_index` (`order_sn`),  KEY `t_unship_province_id_index` (`province_id`),  KEY `t_unship_city_id_index` (`city_id`),  KEY `idx_mall_id_opratus_status_is_deleted_index` (`mall_id`,`oprate_status`,`is_deleted`) USING BTREE,  KEY `idx_batch_id_mall_id_opratus_status_is_deleted_index` (`batch_id`,`mall_id`,`oprate_status`,`is_deleted`) USING BTREE) ENGINE=InnoDB AUTO_INCREMENT=24397264 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci COMMENT='应发未发订单流水表'思路，就是增加联合索引，先把问题解决掉再说。参考文档：http://blog.csdn.net/xifeijian/article/details/19773795