php - 优化 CI 中的 MySQL 查询

Question

我正在使用 Codeigniter + MySQL。我想打印一个部分中每个类别的记录数。我有一个广告表、类别表和部分表。这是我的代码:

foreach($categories as $category){
$query = $this->db->query(" SELECT count(*) AS total_ads from ads where categoryid = $category->id and ( status = 1 OR status = 3 ) and sectionid = $section->id");
$count_row = $query->row();
$count  = $count_row->total_ads;
}

广告总数约为 62138 个(记录)。 但服务器响应时间太长(大约 4 秒)。有没有什么可以加快这段代码的速度，我的意思是进行更改以优化。

Answer 1

尝试在数据库中创建新索引:

CREATE INDEX cat_sec_status ON ads (categoryid, sectionid, status);

并将代码更改为:

$query = $this->db->query("
    SELECT COUNT(id) AS total_ads, categoryid
    FROM ads
    WHERE categoryid IN $categorysIds
        AND sectionid = $section->id            
        AND status IN (1,3)
    GROUP BY categoryid
");

$count_row = $query->row();

在变量 $categorysIds 中，以“(1,2,3,4,5)”格式存储所有类别 ID。 这段代码不需要 foreach。

更新: 最终的代码可能是这样的:

// Extract categories Ids into array
$categoriesIds = array_map(function($object) {return $object->id;}, $categories);

// prepare array to SQL statement
$categoriesIdsCondition = '(' . implode(',', $catIds) . ')';

// 'Good' statuses
$enabledStatuses = array(1, 3); 
$enabledStatusesCondition = '(' . implode(',', $enabledStatuses) . ')';

// Get records count of every category
$query = $this->db->query("
    SELECT COUNT(id) AS total_ads, categoryid
    FROM ads
    WHERE categoryid IN $categoriesIdsCondition
        AND sectionid = $section->id            
        AND status IN $enabledStatusesCondition
    GROUP BY categoryid
");

// If there is any records, store them
if ($query->num_rows() > 0)
{
   $adsCounter = $query->result();
}

// Usage example
foreach($adsCounter as $categoryAds){
    echo "In the category with ID = 
        . {$categoryAds->categoryid}
        . there are
        . {$recordsCounter->total_ads}
        . records";
}