codeigniter，mysql查詢性能問題

Question

我正在使用codeigniter和mysql並應用於具有200 MB內存和1 GB CPU的服務器，在 表中獲得40.000行（index：idx_cat）和44行（index：primary）類別和我需要得到最高的，然後4在每個類別中，這是我的查詢

SELECT id,title,preview,created,image,dummy,name 
FROM 
(
select news.id AS id,news.title AS title,preview,created,news.image,category_id , 
     @num := if(@cat = category_id, @num + 1, 1) as row_number, 
     @cat := category_id as dummy, 
     name,d_order 
from news use index (idx_cat) inner join category b on category_id=b.id 
where 
    news.category_id in (9,8,3,35,57,56,15,58,41,42,43,44,34,52,37,38,36,11) and 
    news.status = 1 
having row_number <= 4 
order by dummy ASC,news.created desc 
) as a 
order by d_order ASC,created DESC 



id select_type  table type possible_keys key  key_len  ref  rows Extra 
1 PRIMARY  <derived2> ALL  NULL NULL NULL NULL **29639** Using filesort 
2 DERIVED  b ALL  PRIMARY,id NULL NULL NULL **44** Using where; Using temporary; Using filesort 
2 DERIVED  news ref  idx_cat  idx_cat  **4** b.id 846  Using where  

，並得到了其他6個簡單的加入像

select id,name from others a inner join b on a.cat_id = b.id 

該網站加載相當快大約1秒或2秒之上，但如果在另一個選項卡中打開，而加載它的速度慢一點5-7s。

奇怪的是，CPU使用率達到100％，內存使用得到了+ _ 40 MB來完成一個視圖（確定沒有其他打開），但CI概要其只是用戶4MB。

我也有加載模型，助手，和圖書館點播只是兩個（網址和形式），我把自動載入文件。

如果我開那麼5到10個窗口它說出來的內存，有你們這個東西是什麼發生任何建議，這是推動我瘋了-_-

Answer 1

爲了減輕內心的選擇的結果的大小，移動選擇和領域name和d_order到外的連接選擇

SELECT id,title,preview,created,image,dummy,name,d_order FROM 
    (
select news.id AS id,news.title AS title,preview,created,news.image,category_id , 
     @num := if(@cat = category_id, @num + 1, 1) as row_number, 
     @cat := category_id as dummy 
from news use index (idx_cat) 
where 
    news.category_id in (9,8,3,35,57,56,15,58,41,42,43,44,34,52,37,38,36,11) and 
    news.status = 1 
having row_number <= 4 
order by dummy ASC,news.created desc 
) as a inner join category b on category_id=b.id 
order by d_order ASC,created DESC 

Problably行的數量仍然很大，但我們已經降低了內存。您選擇的方式需要處理整個新聞表格，然後以非常昂貴的計算方式刪除不需要的行。如果你只是用news.id，cat.id和minimun字段來預選新聞，那麼它可能會更有效率，所以新聞正文中的重要字段不在重選中。

SELECT id,c.title,c.preview,created,c.image,dummy,name,d_order FROM 
    (
select news.id AS id,category_id , 
     @num := if(@cat = category_id, @num + 1, 1) as row_number, 
     @cat := category_id as dummy 
from news use index (idx_cat) 
where 
    news.category_id in (9,8,3,35,57,56,15,58,41,42,43,44,34,52,37,38,36,11) and 
    news.status = 1 
having row_number <= 4 
order by dummy ASC,news.created desc 
) as a 
    inner join category b on category_id=b.id 
    inner join news c on a.id = c.id 
    order by d_order ASC,created DESC 

大概我有一些sintax錯誤，但在這裏寫入有點困難，我沒有數據來測試。希望你明白我發現問題的地步。