Nested mongo query - mongodb

Question

Here is what the data looks like:
{
"_id" : {
"item" : "1",
"state" : "something"
},
"things" : {
"ordered" : 2,
"cost" : 123
}
}
I try to query for all doc of item 1, there are many state for that item. I know i can get that record using db.orders.find({_id:{item:"1", state: "something"}}). But I would like to get all states I try something like db.orders.find({_id:{item:"1", state: {$exists: true}}})
But that doesn't seem to work. What am i doing wrong?

Answer 1

If you want to get the list of all the different states you could use.
db.orders.distinct("_id.state");
If you want to get the list of all the states in your collection
db.orders.find({}, {"_id.state": 1});
I really want to get the things.cost for all the states for a given
item
db.orders.aggregate([
{ $group : {
_id : { item : "$_id.item" , state : "$_id.state"},
cost: { $push : "$things.cost" }
}
}
]);
If you want the sum instead of the elements of the group by use $sum instead of $push
How do i get for certain item?
db.orders.aggregate([
{ $match : { "_id.item" : "YOUR_ID" }},
{ $group : {
_id : { item : "$_id.item" , state : "$_id.state"},
cost: { $push : "$things.cost" }
}
}
]);