node.js使用和尚从数组中获取ID的文档

Question

I'm trying to fetch a few documents from a collection in mongodb with a set of ids

similar to SQLish

SELECT * FROM TABLE WHERE <id> IN [1,3,4]

Here is the code i'm using:

var prodCollection = req.db.get('products');
      prodCollection.find({'-_id':{'$in':["572446507cd5bb7304d75993","572446507cd5bb7304d75994"]}},{}, function(err, docs){
        if(err) throw err;
        res.send(docs);
      });

my setup is a node.js server running on local host using express and monk. i've also tried various versions of the same code with or without single quotes for the IN and _id parameters but with no luck, my returned docs array is always empty. I can confirm my database indeed contain the collection and the docs by accessing it from the console :

> db.products.find()
{ "_id" : ObjectId("572446507cd5bb7304d75993"), "name" : "apples", "quantity" : 20, "checked" : false }
{ "_id" : ObjectId("5724466c7cd5bb7304d75994"), "name" : "bananas", "quantity" : 2, "checked" : false }
{ "_id" : ObjectId("5724467e7cd5bb7304d75995"), "name" : "cerial", "quantity" : 10, "checked" : true }

Answer 1

You are trying to query database using string, where ObjectID is an actual object. To convert string to ObjectID you can use mongoose.Types.ObjectId(string) , I am not sure that this will fix your problem, but it is a step in the right direction.

Answer 2

It seems like both MaxKroshka and Tal Avissar are correct, i managed to make the query work (though for now it still only return only the first item by modifying my code as suggested:

first of all it is true that monk does not require the _id field name to be escaped with the - sign so i replaced it with a normal _id string.

secondly it seems that it is possible to convert from a plain hex id string into a fully fledged id object that can be passed to the query using monks 'collection.id(hexString)' function.

here is my modified code which worked (again, but only returning the first one of the provided array)

var prodCollection = req.db.get('products');
var idObjects = [];

//this was the real magic to get it working, converting string id to object
for(var i=0; i<group.products.length; i++){
    dObjects.push(prodCollection.id(group.products[i]));
}

prodCollection.find({'_id':{$in:idObjects}},{}, function(err, docs){
if(err) throw err;
    res.send(docs);
});