Question

我的应用程序的一部分存在一个巨大的问题。我正在使用SQLAlchemy和MySQL组合，并且大多数工作正常，但有一个痒，永远加载，有时甚至5-6分钟，加载客户列表。该表有大约3000行，对于数据库标准来说应该相当小，而且我在一个稍大的表（25k行）上有一个简单的连接。

SQL Alchemy中的查询如下：

last_inv = db.session.query(Sales.id).order_by(Sales.invoice_date.desc()).filter(Customer.email == Sales.email).limit(1).correlate(Customer)
results = db.session.query(Customer, last_inv.as_scalar()).filter_by(archive=0)

原始SQL看起来像这样：

SELECT customer.id AS customer_id
     , customer.first_name AS customer_first_name
     , customer.middle_name AS customer_middle_name
     , customer.last_name AS customer_last_name
     , customer.email AS customer_email
     , customer.password AS customer_password
     , customer.address1 AS customer_address1
     , customer.address2 AS customer_address2
     , customer.city AS customer_city
     , customer.state AS customer_state
     , customer.zip AS customer_zip
     , customer.country AS customer_country
     , customer.phone AS customer_phone
     , customer.cell_phone AS customer_cell_phone
     , customer.current_plan AS customer_current_plan
     , customer.minutes_current_plan AS customer_minutes_current_plan
     , customer.orig_sales_id AS customer_orig_sales_id
     , customer.sales_id AS customer_sales_id
     , customer.team_id AS customer_team_id
     , customer.refill_date AS customer_refill_date
     , customer.minutes_refill_date AS customer_minutes_refill_date
     , customer.active AS customer_active
     , customer.archive AS customer_archive
     , customer.imported AS customer_imported
     , customer.ipaddress AS customer_ipaddress
     , customer.auto_renewal AS customer_auto_renewal
     , customer.signup_date AS customer_signup_date
     , customer.esn AS customer_esn
     , customer.last_update_date AS customer_last_update_date
     , customer.last_update_by AS customer_last_update_by
     , customer.notes AS customer_notes
     , customer.current_pin AS customer_current_pin
     , customer.minutes_current_pin AS customer_minutes_current_pin
     , customer.security_pin AS customer_security_pin
     , (SELECT sales.id  
          FROM sales 
         WHERE customer.email = sales.email 
         ORDER 
            BY sales.invoice_date DESC LIMIT 1) AS anon_1 
  FROM customer 
 WHERE customer.team_id = 1 
   AND customer.archive = 0

我尝试了很多东西，但这真的开始让我感到绝望。这一切都在亚马逊上运行，htop在运行时显示100％的mysql使用率。关于phpmyadmin的查询的分析器，HeidiSQL显示这是在不到两秒的时间内完成的（当没有被cahce命中时），所以它不是导致这个的实际查询（就像我理解这一点一样公平）。

这是EXPLAIN显示的内容：

id  select_type table   type    possible_keys   key key_len ref rows    Extra
1   PRIMARY customer    ALL NULL    NULL    NULL    NULL    3621    Using where
2   DEPENDENT SUBQUERY  sales   ALL NULL    NULL    NULL    NULL    22619   Using where;    Using filesort

来自phpmyadmin的探查器是here和可视化表示here。

我在EC2上运行一个m1.small实例，内存为1650MB。

我也运行了一个mysqlprofiler，这里是结果before和after我所做的优化。我的my.cnf文件为here。

我尝试在表上运行OPTIMIZE，但由于某种原因，未经优化的表的数量总是98，所以我想我做错了。我使用this脚本，以及phpmyadmin中的原始sql，但没有成功。

Answer 1

尝试创建此多列索引，这可以加快查询速度：

CREATE INDEX sales_eml_invdat ON sales( email, invoice_date );

甚至是三列

CREATE INDEX sales_eml_invdat_id ON sales( email, invoice_date, id );

但仅限于id不是主键列的情况如果id是主键，那么前一个索引就足够了。

----编辑------

对不起，我忘了MySql不像其他DBMS那么聪明它本身无法检测到这种情况，必须明确告诉他如何做到这一点请将子查询重新编入：

SELECT sales.id  
FROM sales 
WHERE customer.email = sales.email 
ORDER BY sales.email DESC, sales.invoice_date DESC 
LIMIT 1

此更改使MySql能够使用( email, invoice_date )索引跳过文件排序，请尝试使用。

MySQL性能不佳

1 个答案: