blocks|key|927|text|您可以使用$$ROOT引用根文档。将该文档的所有字段保存在一个字段中，然后尝试获取该字段(取决于您的客户端系统:+Java、C%2B%2B等)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|928|+[
++++{
++++++++$project:+{
++++++++++++custom_field:+"$obj.obj_field1",
++++++++++++document:+"$$ROOT"

++++++++}
++++},
++++...+//group,+match,+and+whatever...
]|code-block|syntax|javascript|929|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.mongodb.org/manual/reference/aggregation-variables/^0|5|6|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

You can use <a href="http://docs.mongodb.org/manual/reference/aggregation-variables/">$$ROOT</a> to references the root document. Keep all fields of this document in a field and try to get it after that (depending on your client system: Java, C++, ...)

<pre><code> [
 {
 $project: {
 custom_field: "$obj.obj_field1",
 document: "$$ROOT"

 }
 },
 ... //group, match, and whatever...
]
</code></pre>

blocks|key|987|text|根据@Deka回复，对于c#+mongodb+driver+2.5，你可以得到包含以下所有键的分组文档；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|988|var+group+=+new+BsonDocument
{
+{+"_id",+"$groupField"+},
+{+"_document",+new+BsonDocument+{+{+"$first",+"$$ROOT"+}+}+}
};

ProjectionDefinition<BsonDocument>+projection+=+new+BsonDocument{{+"document",+"$_document"}};
var+result+=+await+col.Aggregate().Group(group).Project(projection).ToListAsync();

//+For+demo+first+record+
var+fistItemAsT+=+BsonSerializer.Deserialize<T>(result.ToArray()[0]["document"].AsBsonDocument);|code-block|syntax|javascript|989|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

according to @Deka reply, for c# mongodb driver 2.5 you can get the grouped document with all keys like below;

<pre><code>var group = new BsonDocument
{
 { "_id", "$groupField" },
 { "_document", new BsonDocument { { "$first", "$$ROOT" } } }
};

ProjectionDefinition&lt;BsonDocument&gt; projection = new BsonDocument{{ "document", "$_document"}};
var result = await col.Aggregate().Group(group).Project(projection).ToListAsync();

// For demo first record 
var fistItemAsT = BsonSerializer.Deserialize&lt;T&gt;(result.ToArray()[0]["document"].AsBsonDocument);
</code></pre>

blocks|key|218030|text|要向文档中添加新字段，可以使用$addFields|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|218031|from+docs|218032|对于文档中的所有字段，您可以使用$$ROOT|218033|db.collection.aggregate([

{+"$addFields":+{+"custom_field":+"$obj.obj_field1"+}+},
{+"$group":+{
++++++++_id+:+"$field1",
++++++++data:+{+$push+:+"$$ROOT"+}
++++}}
])|code-block|syntax|javascript|218034|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.mongodb.com/manual/reference/operator/aggregation/group/#group-title-by-author^0|F|A|0|0|9|0|0|G|6|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@]|D|@$9|10|A|11|1|12]]|E|$]]|$1|H|3|I|5|6|7|13|8|@$9|14|A|15|B|C]]|D|@]|E|$]]|$1|J|3|K|5|L|7|16|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|17|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

To add new fields to your document you can use <code>$addFields</code> 

<a href="https://docs.mongodb.com/manual/reference/operator/aggregation/group/#group-title-by-author" rel="nofollow noreferrer">from docs</a>

and to all the fields in your document, you can use <code>$$ROOT</code>

<pre><code>db.collection.aggregate([

{ "$addFields": { "custom_field": "$obj.obj_field1" } },
{ "$group": {
 _id : "$field1",
 data: { $push : "$$ROOT" }
 }}
])
</code></pre>

I would like to define a $project aggregation stage where I can instruct it to add a new field and include all existing fields, without having to list all the existing fields.

My document looks like this, with many fields:

<pre class="lang-json prettyprint-override"><code>{
 obj: {
 obj_field1: "hi",
 obj_field2: "hi2"
 },
 field1: "a",
 field2: "b",
 ...
 field26: "z"
}
</code></pre>

I want to make an aggregation operation like this:

<pre class="lang-json prettyprint-override"><code>[
 {
 $project: {
 custom_field: "$obj.obj_field1",
 //the next part is that I don't want to do
 field1: 1,
 field2: 1,
 ...
 field26: 1
 }
 },
 ... //group, match, and whatever...
]
</code></pre>

Is there something like an "include all fields" keyword that I can use in this case, or some other way to avoid having to list every field separately?

Include all existing fields and add new fields to document

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想定义一个$project聚合阶段，在那里我可以指示它添加一个新字段并包括所有现有字段，而不必列出所有现有字段。我的文档看起来像这样，有很多字段：{    obj: {        obj_field1: "hi",        obj_field2: "hi2"    },    field1: "a",   ...

问包括所有现有字段并向文档中添加新字段
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问包括所有现有字段并向文档中添加新字段
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