Question

Suppose I want to search through a collection, scan the returned result set and return some transformation of it. I’ve tried the following code:

db.my_collection.find({timestamp : {$gt: 1343032491799}}, {_id:0,sid:1}).limit(20).forEach(function(element) { print(element.sid); })

Ok, it worked well. To the question: how can I accumulate the results (sids) into an array instead of just printing them?

Update: ruby-style one-liner is preferred (but not required) of course

Answer 1

Call toArray on the cursor instead of forEach:

var a = db.my_collection.find(
    {timestamp : {$gt: 1343032491799}}, {_id:0,sid:1}).limit(20)
    .toArray().map(function(o){return o.sid;})

UPDATE

Seems you can skip the toArray and go right to the map as the cursor provides that method directly:

var a = db.my_collection.find(
    {timestamp : {$gt: 1343032491799}}, {_id:0,sid:1}).limit(20)
    .map(function(o){return o.sid;})