如何更新文档数组中的对象(嵌套更新) [英] How do you update objects in a document's array (nested updating)

问题描述

假设我们有以下集合，我对此有一些疑问:

Assume we have the following collection, which I have few questions about:

{
    "_id" : ObjectId("4faaba123412d654fe83hg876"),
    "user_id" : 123456,
    "total" : 100,
    "items" : [
            {
                    "item_name" : "my_item_one",
                    "price" : 20
            },
            {
                    "item_name" : "my_item_two",
                    "price" : 50
            },
            {
                    "item_name" : "my_item_three",
                    "price" : 30
            }
    ]
}

1. 我想提高item_name"的价格:my_item_two"如果它不存在，则应将其附加到items"数组.

1. I want to increase the price for "item_name":"my_item_two" and if it doesn't exists, it should be appended to the "items" array.

如何同时更新两个字段?例如，提高my_item_three"的价格；同时增加总数"(具有相同的值).

How can I update two fields at the same time? For example, increase the price for "my_item_three" and at the same time increase the "total" (with the same value).

我更喜欢在 MongoDB 端执行此操作，否则我必须在客户端 (Python) 中加载文档并构建更新的文档并将其替换为 MongoDB 中的现有文档.

I prefer to do this on the MongoDB side, otherwise I have to load the document in client-side (Python) and construct the updated document and replace it with the existing one in MongoDB.

这是我尝试过的并且工作正常如果对象存在:

This is what I have tried and works fine if the object exists:

db.test_invoice.update({user_id : 123456 , "items.item_name":"my_item_one"} , {$inc: {"items.$.price": 10}})

但是，如果密钥不存在，则它什么也不做.此外，它只更新嵌套对象.此命令无法更新总数".领域也是如此.

However, if the key doesn't exist, it does nothing. Also, it only updates the nested object. There is no way with this command to update the "total" field as well.

推荐答案

对于问题 #1，让我们将其分为两部分.首先，增加items.item_name"等于my_item_two"的任何文档.为此，您必须使用位置$"运算符.类似的东西:

For question #1, let's break it into two parts. First, increment any document that has "items.item_name" equal to "my_item_two". For this you'll have to use the positional "$" operator. Something like:

 db.bar.update( {user_id : 123456 , "items.item_name" : "my_item_two" } , 
                {$inc : {"items.$.price" : 1} } , 
                false , 
                true);

请注意，这只会增加任何数组中第一个匹配的子文档(因此，如果数组中有另一个文档item_name"等于my_item_two"，则不会增加).但这可能是您想要的.

Note that this will only increment the first matched subdocument in any array (so if you have another document in the array with "item_name" equal to "my_item_two", it won't get incremented). But this might be what you want.

第二部分比较棘手.我们可以将一个新项目推送到一个没有my_item_two"的数组，如下所示:

The second part is trickier. We can push a new item to an array without a "my_item_two" as follows:

 db.bar.update( {user_id : 123456, "items.item_name" : {$ne : "my_item_two" }} , 
                {$addToSet : {"items" : {'item_name' : "my_item_two" , 'price' : 1 }} } ,
                false , 
                true);

对于您的问题 #2，答案更简单.要在包含my_item_three"的任何文档中增加 item_three 的总数和价格，您可以同时在多个字段上使用 $inc 运算符.类似的东西:

For your question #2, the answer is easier. To increment the total and the price of item_three in any document that contains "my_item_three," you can use the $inc operator on multiple fields at the same time. Something like:

db.bar.update( {"items.item_name" : {$ne : "my_item_three" }} ,
               {$inc : {total : 1 , "items.$.price" : 1}} ,
               false ,
               true);

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