您可以在Mongo中为$ addToSet指定密钥吗? [英] Can you specify a key for $addToSet in Mongo?

问题描述

我有一个文件:

{ 'profile_set' :
  [
    { 'name' : 'nick', 'options' : 0 },
    { 'name' : 'joe',  'options' : 2 },
    { 'name' : 'burt', 'options' : 1 }
  ] 
}

，并希望将新文档添加到profile_set集中(无论该名称如何)(不考虑该选项).

and would like to add a new document to the profile_set set if the name doesn't already exist (regardless of the option).

因此在此示例中，如果我尝试添加:

So in this example if I tried to add:

{'name' : 'matt', 'options' : 0}

它应该添加它，但是添加

it should add it, but adding

{'name' : 'nick', 'options' : 2}

不应执行任何操作，因为即使option是不同的，也已经存在名称为nick的文档.

should do nothing because a document already exists with name nick even though the option is different.

Mongo似乎与整个元素匹配，我最终检查它是否相同，最后我得到

Mongo seems to match against the whole element and I end up with to check if it's the same and I end up with

profile_set containing [{'name' : 'nick', 'options' : 0}, {'name' : 'nick', 'options' : 2}]

是否可以通过$ addToSet来执行此操作，还是必须推送另一个命令?

Is there a way to do this with $addToSet or do I have to push another command?

推荐答案

如果profile_set中已经存在name，则可以使用阻止更新的查询对象来限定update.在外壳中:

You can qualify your update with a query object that prevents the update if the name is already present in profile_set. In the shell:

db.coll.update(
    {_id: id, 'profile_set.name': {$ne: 'nick'}}, 
    {$push: {profile_set: {'name': 'nick', 'options': 2}}})

因此，这只会对具有匹配的_id且没有profile_set元素且name是'nick'的文档执行$push.

So this will only perform the $push for a doc with a matching _id and where there isn't a profile_set element where name is 'nick'.

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