对包含的模型使用limit（） [英] Using limit() on contained model

问题描述

代码

说我有两个模型，分别命名为 Product 和 / code>，它们通过产品hasMany图像和链接到图像belongsTo产品。

现在，假设我要获取所有带有第一张图片的产品。我将使用这个代码：

  $ this-> Products-> find（'all'）
  - > contains（[
'Images'=> function（$ q）{
 return $ q 
  - > order（'created ASC'）
  - > limit （1）; 
} 
]）; 
  

看起来不错，对吧？除了现在只有一个的产品包含图片，但实际上每个产品至少包含一个图片（如果查询没有限制）。

产生的查询

问题似乎是有限制的，因为这会产生以下两个查询（例如）：

  SELECT 
 Products.id AS`Products__id`，
 FROM 
产品产品
  pre> 
 
 
和
  SELECT 
 Images.id AS `Images__id`，
 Images.product_id AS` Images__product_id`，
 Images.created AS`Images__created` 
 FROM 
图像
 WHERE 
 Images.product_id in（1,2,3,4,5）
 ORDER BY 
 created ASC 
 LIMIT 1 
  
查看第二个查询，很明显这将总是只导致一个图像。
 
 
 
问题
 
 
 
但是，当我调用 limit（1）
时，我希望Cake ORM将图像限制为每个产品。
 
 
 
我的问题：这是一个错误，我如何使用ORM？如果是，应如何将图片数量限制为每张图片一张？
解决方案
 
最简单的方法是创建另一个关联：
  $ this-> hasOne FirstImage'，[
'className'=>'Images'，
'foreignKey'=>'image_id'，
'strategy'=>'select'，
 'sort'=> ['FirstImage.created'=>'DESC']，
'conditions'=> function（$ e，$ query）{
 $ query-> limit 1）; 
 return []; 
} 
]）
  
 
The Code

Say I have two models, named Product and Image, which are linked by Product hasMany Image and Image belongsTo Product.

Now, say I want to fetch all products with the first image each. I would use this code:
$this->Products->find('all')
    ->contain([
        'Images' => function($q) {
            return $q
                ->order('created ASC')
                ->limit(1);
        }
    ]);
Looks about right, right? Except now only one of the products contains an image, although actually each product contains at least one image (if queried without the limit).

The resulting Queries

The problem seems to be with the limit, since this produces the following two queries (for example):
SELECT
    Products.id AS `Products__id`,
FROM
    products Products
and
SELECT
    Images.id AS `Images__id`,
    Images.product_id AS `Images__product_id`,
    Images.created AS `Images__created`
FROM
    images Images
WHERE
    Images.product_id in (1,2,3,4,5)
ORDER BY
    created ASC
LIMIT 1
Looking at the second query, it is quite obvious how this will always result in only one image.

The Problem

However, I would have expected the Cake ORM to limit the images to 1 per product when I called limit(1).

My question: Is this an error in how I use the ORM? If so, how should I limit the number of images to one per image?
解决方案
The cleanest way you can do this is by creating another association:
$this->hasOne('FirstImage', [
    'className' => 'Images',
    'foreignKey' => 'image_id',
    'strategy' => 'select',
    'sort' => ['FirstImage.created' => 'DESC'],
    'conditions' => function ($e, $query) {
        $query->limit(1);
        return [];
    }
])


                        
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