CakePHP 和 HABTM 模型限制错误 [英] CakePHP and HABTM Model Limit Error

问题描述

我有一系列具有AndBelongsToMany Media 模型的Post 模型.在 Post 模型内部的某些函数调用中，我不需要检索整个 Media 模型列表.但是，当我使用以下代码时:

I've got a series of Post models that hasAndBelongsToMany Media models. In certain function calls inside of the Post model, I don't need to retrieve the entire list of Media models. However, when I use the following code:

$this->unbindModel( array('hasAndBelongsToMany' => array('Media')) );

// Rebind to get only the fields we need:
$this->bindModel(
        array('hasAndBelongsToMany' => array(
            'Media' => array(
                'className' => 'Media',
                'joinTable' => 'media_posts',
                'foreignKey' => 'post_id',
                'associationForeignKey' => 'media_id',
                'limit' => 1, 
                'fields' => array('Media.type', 'Media.path', 'Media.title')
            )
        )
    )
);
$this->find('all', $params);

此限制仅适用于第一个检索到的 Post 模型之一，并且所有后续 Post 模型都没有关联的媒体:

This limit only works on one of the first retrieved Post model and all following Post models have no associated Media:

Array
(
    [0] => Array
        (
            [Profile] => Array
                (
                )

            [Media] => Array
                (
                    [0] => Array
                        (
                            [type] => photo
                            [path] => ''
                            [title] => ''
                        )

                )
        )

    [1] => Array
        (
            [Profile] => Array
                (
                )

            [Media] => Array
                (
                )

        )

)

任何建议都会很棒.谢谢！

Any suggestions would be great. Thanks!

推荐答案

为什么不使用 containable行为

// you would probably want the next line in the app_model ot be able to use it with all models
$this->Post->actsAs = array('Containable')
$params['conditions'] = array(
);
$params['contain'] = array(
    'Media' => array(
        'fields' => array(
            'type', 'path', 'title'
        ),
        'limit' => 1
    )
);
$this->Post->find('all', $params);

<小时>

刚试过，得到了这个 sql (Module <-> Tag):

---

Just tried that and got this sql (Module <-> Tag):

SELECT `Module`.`id` FROM `modules` AS `Module` WHERE 1 = 1 

和

SELECT `Tag`.`id`, `ModulesTag`.`module_id`, `ModulesTag`.`tag_id` 
FROM `tags` AS `Tag` 
JOIN `modules_tags` AS `ModulesTag` 
  ON (`ModulesTag`.`module_id` IN (1, 2, 3, 4) AND `ModulesTag`.`tag_id` = `Tag`.`id`) 
WHERE `Tag`.`belongs_to` = 'Module' 
ORDER BY `Tag`.`name` ASC 
LIMIT 1

显然不能返回想要的结果，因为您必须对每个模块结果进行查询(这又会导致太多查询).

obviously that cannot return the wanted result, as you would have to do a query for each Module result (which then again would result in way too many queries).

作为结论，我会返回所有标签(在我的示例中)，因为太多结果行的开销比太多查询的开销要好..

As a conclusion I would return all Tags (in my example) as the overhead in too many result rows is better than the overhead of too many queries..

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