我已经失去整晚，试图在下面的查询中获得更好的表现而没有成功：
SELECT COUNT(o.id_offer)
FROM offer o
JOIN offer_product op
ON op.id_offer = o.id_offer
JOIN advertiser a
ON a.id_advertiser = o.id_advertiser
LEFT
JOIN offer_hidden h
ON h.id_offer = o.id_offer
AND h.id_user = 5064
WHERE o.finality = 'sale'
AND h.id_offer IS NULL;
+-------------------+
| COUNT(o.id_offer) |
+-------------------+
| 248250 |
+-------------------+
1 row in set (2.80 sec)
执行大约需要2~4秒。应用程序需要执行大约8~10个类似的查询，因此，毫秒执行时间是必须的。
解释查询：
+------+-------------+---------------+--------+---------------------------------------------------------+-----------------------------+---------+------------------------------+--------+--------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+------+-------------+---------------+--------+---------------------------------------------------------+-----------------------------+---------+------------------------------+--------+--------------------------------------+
| 1 | SIMPLE | offer | ref | PRIMARY,fk_offer_advertiser1_idx,fk_offer_finality1_idx | fk_offer_finality1_idx | 1 | const | 167269 | Using index condition |
| 1 | SIMPLE | offer_product | ref | fk_offer_product_offer1_idx | fk_offer_product_offer1_idx | 4 | db.offer.id_offer | 1 | Using index |
| 1 | SIMPLE | advertiser | eq_ref | PRIMARY | PRIMARY | 4 | db.offer.id_advertiser | 1 | Using index |
| 1 | SIMPLE | offer_hidden | eq_ref | PRIMARY,fk_offer_hidden_user1_idx | PRIMARY | 8 | db.offer.id_offer,const | 1 | Using where; Using index; Not exists |
+------+-------------+---------------+--------+---------------------------------------------------------+-----------------------------+---------+------------------------------+--------+--------------------------------------+
4 rows in set (0.00 sec)
和offer的索引（高基数）：
SHOW INDEXES FROM offer;
+-------+------------+--------------------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+--------------------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| offer | 0 | PRIMARY | 1 | id_offer | A | 352683 | NULL | NULL | | BTREE | | |
| offer | 1 | fk_offer_advertiser1_idx | 1 | id_advertiser | A | 352683 | NULL | NULL | YES | BTREE | | |
| offer | 1 | fk_offer_finality1_idx | 1 | finality | A | 6 | NULL | NULL | | BTREE | | |
+-------+------------+--------------------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
3 rows in set (0.04 sec)
我的开发环境目前有大约30万个优惠和20万个广告商，但生产数据库每个拥有约800万和200万（
）。 SELECT COUNT(*) FROM offer;
+----------+
| COUNT(*) |
+----------+
| 327513 |
+----------+
1 row in set (0.06 sec)
SELECT COUNT(*) FROM advertiser;
+----------+
| COUNT(*) |
+----------+
| 214885 |
+----------+
1 row in set (0.14 sec)
创建表语句：
CREATE TABLE `offer` (
`id_offer` int(11) NOT NULL AUTO_INCREMENT,
`id_advertiser` int(11) unsigned NOT NULL,
`description` text,
`date_offer` datetime NOT NULL,
`finality` enum('buy','sale') NOT NULL,
PRIMARY KEY (`id_offer`),
KEY `fk_offer_advertiser1_idx` (`id_advertiser`),
KEY `fk_offer_finality1_idx` (`finality`),
CONSTRAINT `fk_offer_advertiser1` FOREIGN KEY (`id_advertiser`) REFERENCES `advertiser` (`id_advertiser`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8
我错过了什么吗？
编辑1 - In reply to @Strawberry
CREATE TABLE `advertiser` (
`id_advertiser` int(11) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(200) NOT NULL,
`first_name` varchar(100) DEFAULT NULL,
`last_name` varchar(100) DEFAULT NULL,
`gender` varchar(10) DEFAULT NULL,
`locale` varchar(10) DEFAULT NULL,
`created` datetime NOT NULL,
PRIMARY KEY (`id_advertiser`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8
CREATE TABLE `offer_product` (
`id_offer_product` int(11) NOT NULL AUTO_INCREMENT,
`id_offer` int(11) NOT NULL,
`id_product` int(11) NOT NULL,
PRIMARY KEY (`id_offer_product`),
KEY `fk_offer_product_offer1_idx` (`id_offer`),
KEY `fk_offer_product_product1_idx` (`id_product`),
KEY `fk_offer_product_offer_product1_idx` (`id_offer`,`id_product`),
KEY `fk_offer_product_product_offer1_idx` (`id_product`,`id_offer`),
CONSTRAINT `fk_offer_product_offer1` FOREIGN KEY (`id_offer`) REFERENCES `offer` (`id_offer`) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT `fk_offer_product_product1` FOREIGN KEY (`id_product`) REFERENCES `product` (`id_product`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
CREATE TABLE `offer_hidden` (
`id_offer` int(11) NOT NULL,
`id_user` int(11) NOT NULL,
PRIMARY KEY (`id_offer`,`id_user`),
KEY `fk_offer_hidden_user1_idx` (`id_user`),
CONSTRAINT `fk_offer_hidden_user1` FOREIGN KEY (`id_user`) REFERENCES `user` (`id_user`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8
答案 0 :(得分：0)
您必须设置多列索引：
像这样的东西
ALTER TABLE offer ADD INDEX(finality, id_offer, id_advertiser);
ALTER TABLE offer_product ADD INDEX(id_offer);
ALTER TABLE advertiser ADD INDEX(id_advertiser);
ALTER TABLE offer_hidden ADD INDEX(id_offer, id_user);
这样，您的搜索将首先按结果检索商品，然后使用每个表的索引进行联接
答案 1 :(得分：0)
-- covering index access to 'offer'
-- (and, perhaps, better caching for 'offer_product' too)
ALTER TABLE offer ADD INDEX(finality, id_offer, id_advertiser);
SELECT COUNT(o.id_offer)
FROM (
-- do 'left join' first to minimize number of rows
-- before scanning 'offer_product' and 'advertiser'
SELECT offer.id_offer, offer.id_advertiser
FROM offer
LEFT JOIN offer_hidden h ON
h.id_offer = offer.id_offer
AND h.id_user = 5064
WHERE
offer.finality = 'sale'
AND h.id_offer IS NULL
) o
JOIN offer_product op ON
op.id_offer = o.id_offer
JOIN advertiser a ON
a.id_advertiser = o.id_advertiser
;