我有一个浏览类别查询，我试图优化。我结束了使用临时;在解释和查询中使用filesort在类别为60,000行的类型上很慢。如果我删除Order By子句，查询运行速度非常快.05秒，可以执行60,000行。使用Order By子句非常慢，大约5秒钟。零件包含大约500,000行，Parts_Category也是如此。
我在零件（状态，级别，仓库，更新）上有一个名为sort_index
的组索引在解释的顶部我有|所有|使用临时;使用filesort
所有其他索引显示正常。有人可以告诉我问题可能是什么？我没有想法。也许我应该重新安排这个查询，以便我可以获得更好的表现？
查询。
SELECT Parts.*, Image.type, Image.width, Image.height,
(SELECT name FROM Location_State WHERE id = Parts.state_id) AS state,
(SELECT name FROM Location_Region WHERE id = Parts.region_id) AS region,
(SELECT start_date FROM Promotion WHERE id = Parts.promotion_id) AS promotion_start_date,
(SELECT end_date FROM Promotion WHERE id = Parts.promotion_id) AS promotion_end_date
FROM ( SELECT parts_id FROM Parts_Category WHERE Parts_Category.category_id = '40'
UNION SELECT parts_id FROM Parts_Category WHERE Parts_Category.main_category_id = '40') cid
LEFT JOIN Image ON Parts.image_id = Image.id
JOIN Parts ON Parts.id = cid.parts_id AND Parts.status = 'A'
ORDER BY Parts.level DESC, Parts.warehouse DESC, Parts.updated DESC LIMIT 0, 15
Table structure for table Parts Field Type Null Default id int(11) No auto_increment image_id int(11) Yes 0 gallery_id int(11) Yes 0 image_count int(3) Yes 0 promotion_id int(11) Yes 0 country_id int(11) Yes NULL state_id int(11) Yes NULL region_id int(11) Yes NULL city_id int(11) Yes NULL area_id int(11) Yes NULL updated datetime Yes 0000-00-00 00:00:00 entered datetime Yes 0000-00-00 00:00:00 renewal_date date Yes 0000-00-00 discount_id varchar(10) Yes NULL title varchar(100) Yes search_title varchar(255) Yes warehouse varchar(50) Yes url varchar(255) Yes display_url varchar(255) Yes friendly_url varchar(100) Yes NULL description varchar(255) Yes keywords varchar(1000) Yes NULL attachment_file varchar(255) Yes attachment_caption varchar(255) Yes status char(1) Yes level tinyint(3) Yes 0 worldwide tinyint(1) Yes 0 random_number int(11) Yes NULL reminder tinyint(4) Yes NULL category_search varchar(1000) Yes video_snippet varchar(1000) Yes importID int(11) Yes 0 Indexes PRIMARY 518623 id random_number INDEX 32201 random_number country_id INDEX 1 country_id state_id INDEX 8 state_id region_id INDEX 5 region_id renewal_date INDEX 1 renewal_date worldwide INDEX 1 worldwide friendly_url INDEX 518623 friendly_url promotion_id INDEX 1 promotion_id city_id INDEX 1 city_id area_id INDEX 1 area_id zip_code INDEX 2790 zip_code importID INDEX 518623 importID image_id INDEX 10 image_id -------------- index_browse_category INDEX 52 level status warehouse updated ----------------- keywords FULLTEXT 1 description keywords category_search Parts_Category id int(11) No auto_increment parts_id int(11) No 0 category_id int(11) No 0 main_category_id int(10) No 0 Index PRIMARY PRIMARY 519330 id category_id INDEX 519330 category_id parts_id main_category_id INDEX 519330 main_category_id parts_id
答案 0 :(得分：39)
尝试重写您的查询：
SELECT p.*, i.type, i.width, i.height,
(SELECT name FROM Location_State WHERE id = p.state_id) AS state,
(SELECT name FROM Location_Region WHERE id = p.region_id) AS region,
(SELECT start_date FROM Promotion WHERE id = p.promotion_id) AS promotion_start_date,
(SELECT end_date FROM Promotion WHERE id = p.promotion_id) AS promotion_end_date
FROM parts p
LEFT JOIN
image i
ON i.id = p.image_id
WHERE EXISTS (
SELECT NULL
FROM Parts_Category pc
WHERE pc.category_id = '40'
AND pc.parts_id = p.id
UNION ALL
SELECT NULL
FROM Parts_Category pc
WHERE pc.main_category_id = '40'
AND pc.parts_id = p.id
)
AND p.status = 'A'
ORDER BY
p.status DESC, p.level DESC, p.warehouse DESC, p.updated DESC
LIMIT 15
您需要以下索引才能有效工作：
parts (status, level, warehouse, updated) -- this one you have
parts_category (category_id, parts_id)
parts_category (main_category_id, parts_id)
<强>更新
我刚创建了这样的表：
DROP TABLE IF EXISTS `test`.`image`;
CREATE TABLE `test`.`image` (
`id` int(11) NOT NULL,
`type` int(11) NOT NULL,
`width` int(11) NOT NULL,
`height` int(11) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `test`.`location_region`;
CREATE TABLE `test`.`location_region` (
`id` int(11) NOT NULL,
`name` varchar(20) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `test`.`location_state`;
CREATE TABLE `test`.`location_state` (
`id` int(11) NOT NULL,
`name` varchar(20) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `test`.`parts`;
CREATE TABLE `test`.`parts` (
`id` int(11) NOT NULL,
`status` char(1) NOT NULL,
`level` int(11) NOT NULL,
`warehouse` int(11) NOT NULL,
`updated` int(11) NOT NULL,
`state_id` int(11) NOT NULL,
`region_id` int(11) NOT NULL,
`promotion_id` int(11) NOT NULL,
`image_id` int(11) NOT NULL DEFAULT '1',
PRIMARY KEY (`id`),
KEY `status` (`status`,`level`,`warehouse`,`updated`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `test`.`parts_category`;
CREATE TABLE `test`.`parts_category` (
`id` int(11) NOT NULL,
`parts_id` int(11) NOT NULL,
`category_id` int(11) NOT NULL,
`main_category_id` int(11) NOT NULL,
PRIMARY KEY (`id`),
KEY `ix_pc_cat_parts` (`category_id`,`parts_id`),
KEY `ix_pc_main_parts` (`main_category_id`,`parts_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
DROP TABLE IF EXISTS `test`.`promotion`;
CREATE TABLE `test`.`promotion` (
`id` int(11) NOT NULL,
`start_date` datetime NOT NULL,
`end_date` datetime NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
并填写样本数据：
INSERT
INTO parts
SELECT id,
CASE WHEN RAND() < 0.1 THEN 'A' ELSE 'B' END,
RAND() * 100,
RAND() * 100,
RAND() * 100,
RAND() * 50,
RAND() * 50,
RAND() * 50,
RAND() * 50
FROM t_source
LIMIT 500000;
INSERT
INTO parts_category
SELECT id,
id,
RAND() * 100,
RAND() * 100
FROM t_source
LIMIT 500000;
INSERT
INTO location_state
SELECT id, CONCAT('State ', id)
FROM t_source
LIMIT 1000;
INSERT
INTO location_region
SELECT id, CONCAT('Region ', id)
FROM t_source
LIMIT 1000;
INSERT
INTO promotion
SELECT id,
'2009-07-22' - INTERVAL RAND() * 5 - 20 DAY,
'2009-07-22' - INTERVAL RAND() * 5 DAY
FROM t_source
LIMIT 1000;
上面的查询针对30 milliseconds运行，并产生以下计划：
1, 'PRIMARY', 'p', 'ref', 'status', 'status', '3', 'const', 107408, 'Using where'
1, 'PRIMARY', 'i', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'test.p.image_id', 1, ''
6, 'DEPENDENT SUBQUERY', 'pc', 'ref', 'ix_pc_cat_parts', 'ix_pc_cat_parts', '8', 'const,test.p.id', 1, 'Using index'
7, 'DEPENDENT UNION', 'pc', 'ref', 'ix_pc_main_parts', 'ix_pc_main_parts', '8', 'const,test.p.id', 1, 'Using index'
, 'UNION RESULT', '<union6,7>', 'ALL', '', '', '', '', , ''
5, 'DEPENDENT SUBQUERY', 'Promotion', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'test.p.promotion_id', 1, ''
4, 'DEPENDENT SUBQUERY', 'Promotion', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'test.p.promotion_id', 1, ''
3, 'DEPENDENT SUBQUERY', 'Location_Region', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'test.p.region_id', 1, ''
2, 'DEPENDENT SUBQUERY', 'Location_State', 'eq_ref', 'PRIMARY', 'PRIMARY', '4', 'test.p.state_id', 1, ''
如你所见，没有temporary，没有filesort，一切都很快。
为了帮助您，我只需要看看您的表格是如何定义的。
答案 1 :(得分：1)
John，问题是你的查询被构造成从派生表中选择。派生表无法从您的索引中受益。尝试更新您的查询，如下所示：
SELECT
Parts.*,
Image.type, Image.width, Image.height,
Location_State.name AS state,
Location_Region.name AS region,
Promotion.start_date AS promotion_start_date,
Promotion.end_date AS promotion_end_date
FROM Parts
LEFT JOIN Image ON Parts.image_id = Image.id
LEFT JOIN Location_State ON Parts.state_id = Location_State.id
LEFT JOIN Location_Region ON Parts.state_id = Location_Region.id
LEFT JOIN Promotion ON Parts.promotion_id = Promotion.id
INNER JOIN Parts_Category ON (Parts_Category.category_id = 40 OR Parts_Category.main_category_id = 40)
WHERE Parts.status = 'A'
GROUP BY Parts.id
ORDER BY Parts.level DESC, Parts.warehouse DESC, Parts.updated DESC LIMIT 0, 15
注意，如果您的Location_State，Location_Region，Promotion表不需要LEFT JOIN，那么请使用INNER JOIN。它可能会表现得更好。
要进一步协助优化此查询，请提供以下信息：
SHOW CREATE TABLE Parts;
如果我提供的重写查询与您的示例相同（它应该），那么还提供：
EXPLAIN <my query here>\G