[英]Remove subquery to improve performance
以下查詢非常慢,很可能是子查詢
SELECT *
FROM releases
INNER JOIN release_artists ON release_artists.release_id = releases.id
WHERE release_artists.artists IN (SELECT release_artists.artists
FROM release_artists
INNER JOIN charts_extended ON charts_extended.release_id = release_artists.release_id
WHERE charts_extended.artist = 'Quickinho'
GROUP BY release_artists.artists)
GROUP BY releases.id
ORDER BY releases.date DESC
LIMIT 0,60
charts_extended.artist
有大約2500條記錄,所以這不應該花那么長時間。 我可以使用什么而不是子查詢?
EXPLAIN
給出
1 PRIMARY releases index PRIMARY date 82 NULL 60 Using temporary
1 PRIMARY release_artists ref release_id release_id 4 soundshe.releases.id 1 Using where; Using index
2 DEPENDENT SUBQUERY charts_extended ref artist_2,release_id,artist artist_2 82 const 2472 Using where; Using index; Using temporary; Using filesort
2 DEPENDENT SUBQUERY release_artists ref release_id release_id 4 soundshe.charts_extended.release_id 1 Using index
表DESC
如下
charts_extended
id int(11) NO PRI NULL auto_increment
artist varchar(80) NO MUL NULL
url text NO NULL
release_id int(11) NO MUL NULL
date varchar(50) NO NULL
type varchar(4) NO NULL
source varchar(3) NO NULL
發布
id int(11) NO PRI NULL
artist varchar(255) NO MUL NULL
all_artists varchar(200) NO MUL NULL
format varchar(80) NO MUL NULL
title varchar(255) NO MUL NULL
label varchar(255) NO MUL NULL
label_no_country varchar(255) NO MUL NULL
link text NO NULL
genre varchar(50) NO MUL NULL
date varchar(80) NO MUL NULL
image text NO NULL
favourite varchar(1) NO NULL
time varchar(20) NO NULL
category varchar(30) NO MUL NULL
format_category varchar(20) NO MUL NULL
display varchar(1) NO NULL
image_stored varchar(1) NO NULL
release_artists
id int(11) NO PRI NULL auto_increment
release_id int(10) NO MUL NULL
artists varchar(100) NO NULL
您的子查詢加入到release_artists,但您的外部查詢也是如此,這是不尋常的。 看起來你想要發布藝術家的60個最新版本,圖表擴展arist是Quickinho。 如果我正確理解查詢,我認為你根本不需要子查詢。
我會嘗試
SELECT * FROM releases
INNER JOIN release_artists
ON release_artists.release_id=releases.id
INNER JOIN charts_extended
ON charts_extended.release_id=release_artists.release_id
WHERE charts_extended.artist='Quickinho'
GROUP BY releases.id
ORDER BY releases.date DESC
LIMIT 0,60
您沒有提供有關圖表擴展表的大量信息,但是如果您獲得重復項,因為每個發布藝術家有上述n行,您可以通過調整組或使用不同的等來刪除重復項。
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