最近我有這個question,一切正常,直到我把它發送到我的服務器在DreamHost。如何提高此查詢的性能?
下面的查詢似乎需要太長的時間來執行,我不知道爲什麼這麼多行一次處理。在我的本地服務器中,相同的查詢在0.3秒內執行完畢。
SELECT feed_entries . *
FROM feed_entries
WHERE
id
IN (
SELECT e.id
FROM feed_entries AS e
INNER JOIN feeds AS f ON e.feed_id = f.id
INNER JOIN entries_categorias AS ec ON ec.entry_id = e.id
INNER JOIN categorias AS c ON ec.categoria_id = c.id
WHERE
e.deleted =0
AND
c.slug
IN ('entenda', 'google')
GROUP BY e.id
HAVING COUNT(DISTINCT ec.id) =2
)
ORDER BY date DESC
LIMIT 1
這是我從支持團隊收到的消息:
嗯,它看起來像該查詢 鎖定由於這些其他查詢 像這樣的加工6.5百萬 記錄,持續11秒。
# Query_time: 11.639269 Lock_time: 0.000192 Rows_sent: 2 Rows_examined:
6509098
use desenvolvimentistas;
SET timestamp=1280325753;
SELECT `e`.*, `f`.`titulo` AS `feedTitulo`, `f`.`url` AS `feedUrl` FROM
`feed_entries` AS `e`
INNER JOIN `feeds` AS `f` ON e.feed_id =f.id WHERE (e.id IN (SELECT
`e`.`id` FROM `feed_entries` AS `e`
INNER JOIN `feeds` AS `f` ON e.feed_id =f.id
INNER JOIN `entries_categorias` AS `ec` ON ec.entry_id =e.id
INNER JOIN `categorias` AS `c` ON ec.categoria_id =c.id WHERE (e.deleted
=0) AND (e.id NOT IN ('', '', '842', '853', '774', '878')) AND
(e.imagem145x145 =1) AND (c.slug IN('destaque-2')) GROUP BY `e`.`id`
HAVING (COUNT(DISTINCT ec.id) =1))) ORDER BY `e`.`date` DESC LIMIT 4;
有可能的查詢需要在本地計算機是 空閒的0.3秒到 運行,但因爲它是在 一次運行查詢150這是在我們的服務器上 緩慢,並且每一個正在處理 1530萬條記錄。
我有我們的MySQL管理員看了看 它,他說,這是相當低效 和感到驚訝的是 數據庫甚至訪問,因爲 查詢沒有這麼鎖定。他說 表示數據庫將被禁用,如果 它繼續這種方式並導致 服務器問題。他說你應該修復所檢查的行或者獲得一個MySQL PS,儘管mysql ps不會修復 它,而是隻會阻止 數據庫被禁用。
下面是該查詢:
# Query_time: 25.944779 Lock_time: 0.000176 Rows_sent: 0 Rows_examined:
15378209
use desenvolvimentistas;
SELECT `feed_entries`.* FROM `feed_entries` WHERE (id IN (SELECT `e`.`id`
FROM `feed_entries` AS `e` INNER JOIN `feeds` AS `f` ON e.feed_id =f.id
INNER JOIN `entries_categorias` AS `ec` ON ec.entry_id =e.id INNER JOIN
`categorias` AS `c` ON ec.categoria_id =c.id WHERE (e.deleted =0) AND
(c.slug IN('entenda','google')) GROUP BY `e`.`id` HAVING (COUNT(DISTINCT
ec.id) =2))) ORDER BY `date` DESC LIMIT 1;
這裏是另一個需要被固定:
# Query_time: 27.010857 Lock_time: 0.000165 Rows_sent: 0 Rows_examined:
15382750
use desenvolvimentistas;
SET timestamp=1280325706;
SELECT `e`.*, `f`.`titulo` AS `feedTitulo`, `f`.`url` AS `feedUrl` FROM
`feed_entries` AS `e`
INNER JOIN `feeds` AS `f` ON e.feed_id =f.id WHERE (e.id IN (SELECT
`e`.`id` FROM `feed_entries` AS `e`
INNER JOIN `feeds` AS `f` ON e.feed_id =f.id
INNER JOIN `entries_categorias` AS `ec` ON ec.entry_id =e.id
INNER JOIN `categorias` AS `c` ON ec.categoria_id =c.id WHERE (e.deleted
=0) AND (c.slug IN('manchete', 'google')) GROUP BY `e`.`id` HAVING
(COUNT(DISTINCT ec.id) =2))) ORDER BY `e`.`date` DESC LIMIT 4;7:18
因爲他命令它,但只取得最好的結果,是否有一個好的建議可以有'日期'的索引? – 2010-07-28 15:44:54
@Neil Trodden:是的,但是[MySQL對分配索引的空間有限制(MyISAM爲1,000,InnoDB爲767)](http://dev.mysql.com/doc/refman/5.0/en/create-index .html)所以JOIN標準是我的首要任務,然後看看我能做些什麼來覆蓋索引。 – 2010-07-28 15:59:19
謝謝,我減少了150個查詢的數量並定義了索引。也發現了其他的錯誤。現在可以了。 – 2010-08-03 16:12:23