(使用MySQL 4.1.22)幫助優化MySQL查詢
我不能讓我的這個查詢在大表上使用索引(200K +行),它做就可以了全表掃描。查詢現在需要大約1.2秒。如果可能,我想把它縮短到不到0.2秒。
這裏是我的查詢:
SELECT st_issues.issue_id, st_issues.cat_id,st_categories.name AS cat_name, st_issues.status_id,st_statuses.name AS status_name, st_issues.priority_id,st_priorities.name AS priority_name,st_priorities.color AS color, st_issues.assigned_cid,assigned_u.firstname,assigned_u.lastname,assigned_u.screenname, message, rating, created_by_email,created_by_cid,created_by_uid,by_user.firstname AS by_firstname,by_user.lastname AS by_lastname,by_user.screenname AS by_screenname, st_issues.browser,from_url,created_by_store,created,st_issues.stamp
FROM st_issues
JOIN st_categories ON (st_issues.cat_id=st_categories.cat_id)
JOIN st_statuses ON (st_issues.status_id=st_statuses.status_id)
JOIN st_priorities ON (st_issues.priority_id=st_priorities.priority_id)
LEFT JOIN users AS assigned_u ON (assigned_u.cid=st_issues.assigned_cid)
LEFT JOIN users AS by_user ON (by_user.uid=st_issues.created_by_uid)
LEFT JOIN st_issue_changes ON (st_issues.issue_id=st_issue_changes.issue_id AND change_id=0)
WHERE st_issues.assigned_cid=0
解釋的結果:
1, 'SIMPLE', 'st_issues', 'ALL', '', '', , '', 4, 'Using where'
1, 'SIMPLE', 'st_categories', 'eq_ref', 'PRIMARY', 'PRIMARY', 1, 'sg.st_issues.cat_id', 1, ''
1, 'SIMPLE', 'st_priorities', 'eq_ref', 'PRIMARY', 'PRIMARY', 1, 'sg.st_issues.priority_id', 1, ''
1, 'SIMPLE', 'assigned_u', 'ref', 'cid', 'cid', 8, 'sg.st_issues.assigned_cid', 1, ''
1, 'SIMPLE', 'st_statuses', 'ALL', 'PRIMARY', '', , '', 4, 'Using where'
1, 'SIMPLE', 'by_user', 'ALL', '', '', , '', 221623, ''
1, 'SIMPLE', 'st_issue_changes', 'eq_ref', 'PRIMARY', 'PRIMARY', 6, 'sg.st_issues.issue_id,const', 1, ''
顯然問題出在加入上「by_user」,因爲它不使用索引。
下面是一些「用戶」表的定義:
CREATE TABLE `users` (
`cid` double unsigned NOT NULL auto_increment,
`uid` varchar(20) NOT NULL default '',
...
`firstname` varchar(20) default NULL,
`lastname` varchar(20) default NULL,
...
PRIMARY KEY (`uid`),
...
) ENGINE=InnoDB
任何人有爲什麼它不使用連接中的主鍵的任何想法?
任何人有任何想法或提示如何加快此查詢更多?
(我可以添加其他表的表定義,如果需要/想)
編輯:
這裏是st_issues表定義:
CREATE TABLE `st_issues` (
`issue_id` int(10) unsigned NOT NULL auto_increment,
`cat_id` tinyint(3) unsigned NOT NULL default '0',
`status_id` tinyint(3) unsigned NOT NULL default '0',
`priority_id` tinyint(3) unsigned NOT NULL default '0',
`assigned_cid` int(10) unsigned NOT NULL default '0',
`rating` tinyint(4) default NULL,
`created_by_email` varchar(255) NOT NULL default '',
`created_by_cid` int(10) unsigned NOT NULL default '0',
`created_by_uid` varchar(20) NOT NULL default '',
`created_by_store` tinyint(3) unsigned NOT NULL default '0',
`browser` varchar(255) NOT NULL default '',
`from_url` varchar(255) NOT NULL default '',
`created` datetime NOT NULL default '0000-00-00 00:00:00',
`stamp` datetime NOT NULL default '0000-00-00 00:00:00',
PRIMARY KEY (`issue_id`),
KEY `idx_create_by_cid` (`created_by_cid`),
KEY `idx_create_by_uid` (`created_by_uid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
你對st_issues有什麼索引? – 2009-09-19 15:40:11
您定義了哪些索引? – 2009-09-19 15:40:13
我剛剛添加了st_issues的定義 – Echo 2009-09-19 15:44:40