Get document based on multiple criteria of embedded collection - mongodb

Question

I have the following document, I need to search for multiple items from the embedded collection"items".
Here's an example of a single SKU
db.sku.findOne()
{
"_id" : NumberLong(1192),
"description" : "Uploaded via CSV",
"items" : [
{
"_id" : NumberLong(2),
"category" : DBRef("category", NumberLong(1)),
"description" : "840 tag visual",
"name" : "840 Visual Mini Round",
"version" : NumberLong(0)
},
{
"_id" : NumberLong(7),
"category" : DBRef("category", NumberLong(2)),
"description" : "Maxi",
"name" : "Maxi",
"version" : NumberLong(0)
},
{
"_id" : NumberLong(11),
"category" : DBRef("category", NumberLong(3)),
"description" : "Button",
"name" : "Button",
"version" : NumberLong(0)
},
{
"_id" : NumberLong(16),
"category" : DBRef("category", NumberLong(4)),
"customizationFields" : [
{
"_class" : "CustomizationField",
"_id" : NumberLong(1),
"displayText" : "Custom Print 1",
"fieldName" : "customPrint1",
"listOrder" : 1,
"maxInputLength" : 12,
"required" : false,
"version" : NumberLong(0)
},
{
"_class" : "CustomizationField",
"_id" : NumberLong(2),
"displayText" : "Custom Print 2",
"fieldName" : "customPrint2",
"listOrder" : 2,
"maxInputLength" : 17,
"required" : false,
"version" : NumberLong(0)
}
],
"description" : "2 custom lines of farm print",
"name" : "Custom 2",
"version" : NumberLong(2)
},
{
"_id" : NumberLong(20),
"category" : DBRef("category", NumberLong(5)),
"description" : "Color Red",
"name" : "Red",
"version" : NumberLong(0)
}
],
"skuCode" : "NF-USDA-XC2/SM-BC-R",
"version" : 0,
"webCowOptions" : "840miniwithcust2"
}
There are repeat items.id throughout the embedded collection. Each Sku is made up of multiple items, all combinations are unique, but one item will be part of many Skus.
I'm struggling with the query structure to get what I'm looking for.
Here are a few things I have tried:
db.sku.find({'items._id':2},{'items._id':7})
That one only returns items with the id of 7
db.sku.find({items:{$all:[{_id:5}]}})
That one doesn't return anything, but it came up when looking for solutions. I found about it in the MongoDB manual
Here's an example of a expected result:
sku:{ "_id" : NumberLong(1013),
"items" : [ { "_id" : NumberLong(5) },
{ "_id" : NumberLong(7) },
{ "_id" : NumberLong(12) },
{ "_id" : NumberLong(16) },
{ "_id" :NumberLong(2) } ] },
sku:
{ "_id" : NumberLong(1014),
"items" : [ { "_id" : NumberLong(5) },
{ "_id" : NumberLong(7) },
{ "_id" : NumberLong(2) },
{ "_id" : NumberLong(16) },
{ "_id" :NumberLong(24) } ] },
sku:
{ "_id" : NumberLong(1015),
"items" : [ { "_id" : NumberLong(5) },
{ "_id" : NumberLong(7) },
{ "_id" : NumberLong(12) },
{ "_id" : NumberLong(2) },
{ "_id" :NumberLong(5) } ] }
Each Sku that comes back has both a item of id:7, and id:2, with any other items they have.
To further clarify, my purpose is to determine how many remaining combinations exist after entering the first couple of items.
Basically a customer will start specifying items, and we'll weed it down to the remaining valid combinations. So Sku.items[0].id=5 can only be combined with items[1].id=7 or items[1].id=10 …. Then items[1].id=7 can only be combined with items[2].id=20 … and so forth
The goal was to simplify my rules for purchase, and drive it all from the Sku codes. I don't know if I dug a deeper hole instead.
Thank you,

Answer 1

On the part of extracting the sku with item IDs 2 and 7, when I recall correctly, you have to use $elemMatch:
db.sku.find({'items' :{ '$all' :[{ '$elemMatch':{ '_id' : 2 }},{'$elemMatch': { '_id' : 7 }}]}} )
which selects all sku where there is each an item with _id 2 and 7.

Answer 2

You can use aggregation pipelines
db.sku.aggregate([
{"$unwind": "$sku.items"},
{"$group": {"_id": "$_id", "items": {"$addToSet":{"_id": "$items._id"}}}},
{"$match": {"items._id": {$all:[2,7]}}}
])