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问题描述
我可以以某种方式添加具有静态(未计算)值的自定义字段吗?
Can I somehow add custom field with static (not computed) value?
我想在发送之前准备对象,并且需要删除一些带有内部信息的字段并添加带有某些实体ID的字段.
I want to prepare objects before send and I need to remove some fields with internal information and add field with some entity ID.
例如,我有类似这样的对象的测试"集合
For example I have collection "test" with objects like this
{_id: ObjectId(...), data: {...}}我需要将其转换为
{data: {...}, entity_id: 54}那么如何在不循环生成代码的情况下添加entity_id:54?
So how can I add entity_id: 54 without looping over result in my code?
db.test.aggregate({ $project: {_id: 0, data: 1, entity_id: ? } })谢谢
推荐答案请注意,$ literal是在Mongo 2.6中实现的. 所以现在您可以简单地编写:
Note that $literal was implemented in Mongo 2.6. So now you can simply write:
db.test.aggregate( {$project: {_id: 0, data: 1, entity_id: {$literal: 54}}})请参见 $ literal .
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MongoDB:聚合具有静态值的$ project add字段
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