Remove nested document with condition in MongoDB

问题

For the following JSON how do I remove the dog whose height is the least

{
   _id:0
   "name":"Andy",
   "pets":[
      {
         "type":"dog","name":"max","height":120
      },
      {
         "type":"dog","name":"rover","height":44
      },
      {
         "type":"dog","name":"katie","height":100
      },
      {
         "type":"cat","name":"minni"
      }
   ]
}

回答1:

The problem is the array of subdocuments is not a collection, you can't sort or do something else on it. But if you have an access to any language interface like JavaScript or else it's possible. You just need to extract list of subdocuments, sort them by height, remember the first one and then run the command to pull it from the array based on its name and height. It can be done for example using this JavaScript code right in the MongoDB shell:

var min = 0; var name = "";
db.animals.find({ query:{"_id" : 0} }).forEach(
function(record){
    var sets = record.pets; 
    min = sets[0].height;
    sets.forEach(function(set){
        if(set.height <= min) 
            {min=set.height;
            name=set.name;}
            });
    print(min);
    print(name);    
    query = {"_id": 0}
    update = { "$pull" : { "pets" : { "name" : name } } };
    db.animals.update(query, update);
    })

I suspect the solution is not the most elegant but anyway it works.

来源：https://stackoverflow.com/questions/13388791/remove-nested-document-with-condition-in-mongodb