MySQL性能不佳

Question

我的應用程序的一部分存在一個大問題。我使用的是SQLAlchemy和MySQL的組合，並且大部分的工作都很好，但是有一個癢會持續加載，有時甚至5-6分鐘，載入客戶列表。該表大約有3000行，這對於數據庫標準來說應該是相當小的，並且我在一個稍大的表格（25k行）上有一個簡單的連接。

在SQL鍊金術查詢如下：

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看起來是這樣的：

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 

我已經試過無數的事情，但這是真的開始讓我感到絕望。這一切都在亞馬遜上運行，並且htop在運行時顯示100％的MySQL使用率。 Profiler對phpmyadmin進行查詢時，HeidiSQL顯示它在不到兩秒的時間內完成（當不在cahce中查找時），所以它不是實際的查詢造成的（正如我理解的那樣）。

這是EXPLAIN顯示：

從phpmyadmin的

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 

Profiler是here和視覺表現here。

我在EC2上運行一個m1.small實例，內存爲1650MB。

我也運行了一個mysqlprofiler，以下是結果before和after我所做的優化。我的my.cnf文件是here。

我已經嘗試在表上運行OPTIMIZE，但由於某種原因未優化的表的數量總是98，所以我想我做錯了什麼。我使用this腳本，以及phpmyadmin中的原始sql，但沒有成功。

任何幫助表示讚賞，謝謝閱讀！

Answer 1

嘗試創建這個多列索引，這應該加快查詢更多：

CREATE INDEX sales_eml_invdat ON sales(email, invoice_date); 

上三列

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

但只有在一個情況下

甚至當id不是主鍵柱。
如果id是主鍵，那麼前一個索引就足夠了。

---- ------編輯

我很抱歉，我忘了MySQL是沒有那麼聰明的人DBMS。
它不能自己檢測到這種情況，必須明確告訴他如何去做。
請rewrtite子查詢到：

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

這種變化使MySQL使用(email, invoice_date)指數跳過文件排序，請試試吧。