Question

Mysql服务器设置为缓存：

query_cache_size = 1G
query_cache_type = 1

当我从phpmyadmin执行查询时，第一次查询需要2秒，第二次执行0.0001秒。

因此缓存确实有效。但是在php脚本中，查询每次都会持续2秒。

php version 5.4.14
mysql 5.5.30

脚本：

<?php
    $db = new mysqli("localhost", "user", "pass", "search");
    $t = microtime(true);
    $res = $db-> query("SELECT 
                            i.page_id, 
                            SUM(i.weight) as w 
                        FROM
                            search.search_index i 
                        INNER JOIN 
                            search.word_full w1 
                            ON w1.word=i.word 
                        INNER JOIN 
                            search.word_full w2 
                            ON w1.word_base=w2.word_base 
                        WHERE 
                            w2.word = 'api' 
                        GROUP BY 
                            i.page_id 
                        ORDER BY NULL");
    print($res->num_rows."\n");
    print(microtime(true) - $t);
?>

<?php
    $link = mysql_connect("localhost", "root", "pass");
    mysql_select_db("search");

    $t = microtime(true);
    $res = $db-> query("SELECT 
                            i.page_id, 
                            SUM(i.weight) as w 
                        FROM
                            search.search_index i 
                        INNER JOIN 
                            search.word_full w1 
                            ON w1.word=i.word 
                        INNER JOIN 
                            search.word_full w2 
                            ON w1.word_base=w2.word_base 
                        WHERE 
                            w2.word = 'api' 
                        GROUP BY 
                            i.page_id 
                        ORDER BY NULL");
    print(mysql_num_rows($res)."\n");
    print(microtime(true) - $t);
?>

如果我试试这个：

    $t = microtime(true);
    $res = $db-> query("SELECT 
                            i.page_id, 
                            SUM(i.weight) as w 
                        FROM
                            search.search_index i 
                        INNER JOIN 
                            search.word_full w1 
                            ON w1.word=i.word 
                        INNER JOIN 
                            search.word_full w2 
                            ON w1.word_base=w2.word_base 
                        WHERE 
                            w2.word = 'api' 
                        GROUP BY 
                            i.page_id 
                        ORDER BY NULL");
    print(mysql_num_rows($res)."\n");
    print(microtime(true) - $t."\n");

    $t = microtime(true);
    $res = $db-> query("SELECT 
                            i.page_id, 
                            SUM(i.weight) as w 
                        FROM
                            search.search_index i 
                        INNER JOIN 
                            search.word_full w1 
                            ON w1.word=i.word 
                        INNER JOIN 
                            search.word_full w2 
                            ON w1.word_base=w2.word_base 
                        WHERE 
                            w2.word = 'api' 
                        GROUP BY 
                            i.page_id 
                        ORDER BY NULL");
    print(mysql_num_rows($res)."\n");
    print(microtime(true) - $t."\n");
?>

脚本返回

235899
1.8554458618164
235899
1.8542320728302

Mysql缓存也不起作用。

表格结构：

CREATE TABLE IF NOT EXISTS `search_index` (
  `page_id` varchar(32) NOT NULL,
  `word` varchar(32) NOT NULL,
  `weight` int(11) NOT NULL,
  PRIMARY KEY (`word`,`page_id`),
  KEY `page_id` (`page_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;



CREATE TABLE IF NOT EXISTS `word_full` (
  `word` varchar(32) NOT NULL,
  `word_base` varchar(32) NOT NULL,
  PRIMARY KEY (`word`,`word_base`),
  UNIQUE KEY `word_base` (`word_base`,`word`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Answer 1

PHP中的每个调用都是一个新实例，与前一个实例无关。除非你明确声明它。

查看查询缓存：http://php.net/manual/en/mysqlnd-qc.quickstart.caching.php

Answer 2

我假设word_full.word_base和word_full.word都是VARCHAR列。如果不是这种情况，请提供完整的表结构，包括search_index和word_full表的键。

我会

将wordID列添加到word_full（INT UNSIGNED AUTO_INCREMENT NOT NULL）并将其设为主要KEy
在word_full.word上添加一个UNIQUE键
将word_base更改为引用wordID（现在wordID和word_base都是数字）
为word_full.word_base添加密钥
将search_index.word更改为search_index.wordID
为search_index.wordID

更改单词以运行数字键将允许MySQL更有效地使用索引。目前（我假设）您将加入一个varchar列两次，然后搜索varchar列。这是非常低效的。

最后，将WHERE移动到JOIN中可能会允许它在不同的点减少行，因此有效地更加优化。这给出了

SELECT 
    i.page_id, 
    SUM(i.weight) as w 

FROM search.search_index i 

INNER JOIN search.word_full w1 
    ON w1.wordID = i.wordID

INNER JOIN search.word_full w2 
    ON w1.wordID_base = w2.wordID_base 
    AND w2.word = 'api' 

GROUP BY i.page_id 
ORDER BY NULL

Answer 3

phpmyadmin修改查询

SELECT 
    i.page_id, 
    SUM(i.weight) as w 
FROM
    search.search_index i 
INNER JOIN 
    search.word_full w1 
    ON w1.word=i.word 
INNER JOIN 
    search.word_full w2 
    ON w1.word_base=w2.word_base 
WHERE 
    w2.word = 'api' 
GROUP BY 
    i.page_id 
ORDER BY NULL

到

SELECT 
    i.page_id, 
    SUM(i.weight) as w 
FROM
    search.search_index i 
INNER JOIN 
    search.word_full w1 
    ON w1.word=i.word 
INNER JOIN 
    search.word_full w2 
    ON w1.word_base=w2.word_base 
WHERE 
    w2.word = 'api' 
GROUP BY 
    i.page_id 
ORDER BY NULL
LIMIT 0, 30

在查询结束时添加 LIMIT 0,30 。

查询大小＆gt; query_cache_limit

我将query_cache_limit增加到10M。

来自php的SQL查询不使用mysql缓存

3 个答案: