我一直在努力提高我的一个数据库(MySQL)查询的性能 . 事情就是我做的,我的表现仍然很慢 . 在我的更改之前,Query运行在9.54s,并且在一些索引更改之后,性能提高到5.67s .
这是我的查询:
Query_time:5.343565 Lock_time:0.000302 Rows_sent:100005 Rows_examined:200017
码:
SET timestamp=1455032448;
SELECT
id,
description,
unit_price,
(SELECT coalesce(sum(quantity),0) from si_invoice_items where product_id = si_products.id) as qty_out ,
(SELECT coalesce(sum(quantity),0) from si_inventory where product_id = si_products.id) as qty_in ,
(SELECT coalesce(reorder_level,0)) as reorder_level ,
(SELECT qty_in - qty_out ) as quantity,
(SELECT (CASE WHEN enabled = 0 THEN 'Disabled' ELSE 'Enabled' END )) AS enabled
FROM
si_products
WHERE
visible = 1
AND domain_id = '1'
ORDER BY
description asc;
这是受影响的所有表的索引信息:
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type
si_products 0 PRIMARY 1 id A 100005 NULL NULL BTREE
si_products 0 PRIMARY 2 domain_id A 100005 NULL NULL BTREE
si_products 1 unit_price 1 unit_price A 10000 NULL NULL YESBTREE
si_products 1 description 1 id A 100005 NULL NULL BTREE
si_products 1 description 2 description A 100005 15 NULL BTREE
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
si_inventory 0 PRIMARY 1 domain_id A NULL NULL NULL BTREE
si_inventory 0 PRIMARY 2 id A 0 NULL NULL BTREE
si_inventory 1 product_id 1 product_id A NULL NULL NULL BTREE
si_inventory 1 quantity 1 quantity A NULL NULL NULL BTREE
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
si_invoice_items 0 PRIMARY 1 id A NULL NULL NULL BTREE
si_invoice_items 0 PRIMARY 2 invoice_id A 7 NULL NULL BTREE
si_invoice_items 1 unit_price 1 unit_price A NULL NULL NULL YES BTREE
si_invoice_items 1 quantity 1 quantity A NULL NULL NULL BTREE
si_invoice_items 1 product_id 1 product_id A NULL NULL NULL YES
任何建议将不胜感激 .
随着我的最后一次改变有所改善
Query_time:3.723339 Lock_time:0.000254 Rows_sent:100005 Rows_examined:200024 Rows_affected:0
SET timestamp=1455037952;
SELECT
A.id,
A.description,
A.unit_price,
(SELECT coalesce(sum(B.quantity),0) from si_invoice_items B JOIN si_products A ON B.product_id = A.id) as qty_out ,
(SELECT coalesce(sum(C.quantity),0) from si_inventory C JOIN si_products A ON C.product_id = A.id) as qty_in ,
(SELECT coalesce(A.reorder_level,0)) as reorder_level ,
(SELECT qty_in - qty_out ) as quantity,
(CASE WHEN A.enabled = 0 THEN 'Disabled' ELSE 'Enabled' END ) AS enabled
FROM
si_products A
WHERE
A.visible = 1
AND A.domain_id = '1'
ORDER BY
description asc;
谢谢Ollie,我已经尝试用您的建议测试Query,但显然没有改善响应时间 .
这是您的方法的结果:
# Query_time: 4.041339 Lock_time: 0.000245 Rows_sent: 100005 Rows_examined: 200029
# Rows_affected: 0
SET timestamp=1455045101;
SELECT p.id, p.description, p.unit_price,
COALESCE(invoice.quantity,0) as qty_out,
COALESCE(inventory.quantity,0)as qty_in,
coalesce(p.reorder_level,0) as reorder_level ,
(select qty_in - qty_out ) as quantity
FROM si_products p
LEFT JOIN (
SELECT SUM(quantity) quantity, product_id
FROM si_invoice_items
GROUP BY product_id
) invoice ON p.id = invoice.product_id
LEFT JOIN (
SELECT SUM(quantity) quantity, product_id
FROM si_inventory
GROUP BY product_id
) inventory ON p.id = inventory.product_id
WHERE p.visible = 1
AND p.domain_id = '1'
ORDER BY
description asc;
3 回答
由于您提供了多少(
Rows_sent: 100005
),查询不能非常快 .这些索引中的任何一个都可能有助于一些:
前两个字段可能有助于过滤;第三个应该防止
ORDER BY
需要"filesort" .当表达式足够时,不要使用子查询 . 例如:
如需进一步讨论,请提供
SHOW CREATE TABLE
和EXPLAIN SELECT...
.您可以重构此查询以消除相关子查询(SELECT子句中的嵌套SELECT) . 如果使用JOINed summary子查询替换这些相关子查询,则性能可能会提高 .
看起来您需要
si_invoice_items
和si_inventory
表的摘要 .您可以使用以下子查询获取这些摘要:
和
然后,您可以将这两个子查询视为虚拟表,并将它们连接到
si_products
表 . 请注意,您需要使用LEFT JOIN,因为您的某些si_products
行可能在其他表中没有匹配的行 .像这样 .
这将只运行两个表上的摘要,然后加入它们 . 所以它应该运行得更快 .
Edit 您正在使用此查询获取超过100K行 . 这是一个非常大的结果集,无论如何都需要一段时间 .
通过在清单和发票表的
(product_id, quahtity)
列上定义复合索引,可以使摘要(GROUP BY)子查询更快 .通过在
(visible, domain_id)
列上定义复合索引,可以更快地从product表中选择记录 .但是你的应用程序仍然需要研磨十万行 .
我找不到比此查询更好的结果:
Query_time:3.174778 Lock_time:0.000250 Rows_sent:100005 Rows_examined:200024
Rows_affected:0