MongoDB find where key equals string from array

Question

I am trying to find in a collection all of the documents that have the given key equal to one of the strings in an array.

Heres an example of the collection.

{
  roomId = 'room1',
  name = 'first'
},
{
  roomId = 'room2',
  name = 'second'
},
{
  roomId = 'room3',
  name = 'third'
}

And heres an example of the array to look through.

[ 'room2', 'room3' ]

What i thought would work is...

collection.find({ roomId : { $in : [ 'room2', 'room3' ]}}, function( e, r )
{
  // r should return the second and third room
});

How can i achieve this?

One way this could be solve would be to do a for loop...

var roomIds = [ 'room2', 'room3' ];
for ( var i=0; i < roomIds.length; i++ )
{
  collection.find({ id : roomIds[ i ]})
}

But this is not ideal....

Are these standalone documents or are they embedded into some "hotel" document? What do you actually get as a result? — Sergio Tulentsev
– Sergio Tulentsev, Commented Jun 7, 2012 at 13:44

mnemosyn · Accepted Answer · 2012-06-07 14:06:02Z

7

What you posted should work - no looping required. The $in operator does the job:

> db.Room.insert({ "_id" : 1, name: 'first'});
> db.Room.insert({ "_id" : 2, name: 'second'});
> db.Room.insert({ "_id" : 3, name: 'third'});
> // test w/ int
> db.Room.find({ "_id" : { $in : [1, 2] }});
{ "_id" : 1, "name" : "first" }
{ "_id" : 2, "name" : "second" }
> // test w/ strings
> db.Room.find({ "name" : { $in : ['first', 'third'] }});
{ "_id" : 1, "name" : "first" }
{ "_id" : 3, "name" : "third" }

Isn't that what you expect?

Tested w/ MongoDB 2.1.1

edited Jun 7, 2012 at 14:06

answered Jun 7, 2012 at 13:49

mnemosyn

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2 Comments

cnotethegr8 Over a year ago

Ahh your correct, it is working... It appears the query is working but the update i had in mind is not. I want that each room in the array is found, (which currently is working) and that they are all updated with { $addToSet : { members : member.id }}. But the update is not working. It appears only the first item found is being updated. How can i change this?

cnotethegr8 Over a year ago

Ahh found it, i use { multi : true }. Thanks for getting me in the right direction.

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