javascript - Object.keys, how to get a list of keys in mongodb - Stack Overflow

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{
"_id": "1",
"style": "13123",
"category": "dress",
"colors": {
    "Black": {
        "prestock": 50,
        "instock": 60,
        "inactive": 0
        },
    "Blue": {
        "prestock": 30,
        "instock": 0,
        "inactive": 0
        },
    "Red": {
        "prestock": 10,
        "instock": 60,
        "inactive": 0
        }
  }
}

i have above json, i need to access to prestock, instock, and inactive. but colors' value will change depending on styles. for example:

{
 "_id": "2",
 "style": "14321", 
 "category": "top",
 "colors": {
     "Green": {
        "prestock": 50,
        "instock": 60,
        "inactive": 0
         }, 
     "Yellow": {
        "prestock": 50,
        "instock": 60,
        "inactive": 0
         }
      }
}

how can i query this in mongodb? would this something that's related to Object.keys(obj)?

ps.if this is a duplicate question please guide me!

Thanks!

{
"_id": "1",
"style": "13123",
"category": "dress",
"colors": {
    "Black": {
        "prestock": 50,
        "instock": 60,
        "inactive": 0
        },
    "Blue": {
        "prestock": 30,
        "instock": 0,
        "inactive": 0
        },
    "Red": {
        "prestock": 10,
        "instock": 60,
        "inactive": 0
        }
  }
}

i have above json, i need to access to prestock, instock, and inactive. but colors' value will change depending on styles. for example:

{
 "_id": "2",
 "style": "14321", 
 "category": "top",
 "colors": {
     "Green": {
        "prestock": 50,
        "instock": 60,
        "inactive": 0
         }, 
     "Yellow": {
        "prestock": 50,
        "instock": 60,
        "inactive": 0
         }
      }
}

how can i query this in mongodb? would this something that's related to Object.keys(obj)?

ps.if this is a duplicate question please guide me!

Thanks!

• javascript
• node.js
• mongodb
• mongodb-query

Share Improve this question Follow asked Oct 10, 2013 at 16:22 whoAmi21whoAmi21 10511 gold badge55 silver badges1414 bronze badges 5

• what do you want to get from it? – Sathya Commented Oct 10, 2013 at 16:28
• @user10 i need to access the values of prestock, instock, and inactive – whoAmi21 Commented Oct 10, 2013 at 16:43
• accessing the values isn't hard once you have the object in your code, you can use javascript there. If you want to query it, you'd have to know what you want to query, i.e. the instock value of the Green or the Yellow ones? Or do you want sth. like 'any color with instock > 0'? In that case, you'd better change the schema. – mnemosyn Commented Oct 10, 2013 at 17:11
• @mnemosyn i need something like this: {"colors.anycolor":{"prestock":{$gte:30}}} – whoAmi21 Commented Oct 10, 2013 at 17:47
• @wisleans You can't query like that, which is why you should probably stick to using an array like mnemosyn suggested in his answer. – JohnnyHK Commented Oct 10, 2013 at 18:51

Add a ment  | 

3 Answers 3

Sorted by: Reset to default 2

A query like {"colors.*.prestock" : {$gte:30}} isn't possible according to SERVER-267, and I doubt this will be supported in the next years.

Your best bet is to change the schema to an array:

colors: [
 { "color" : "Green", "instock" : 50, ... },
 { "color" : "Yellow", "instock" : 50, ... },
]

Then you can query

db.foo.find( {"colors.prestock" : {$gte:30}} )

Note that this will return the entire object, including all colors, i.e. also those for which the query constraint doesn't hold. This could be solved using the aggregation framework, but again, only using $unwind which also requires colors to be an array.

Is this is what you are looking for? MongoDB Get names of all keys in collection

If not, then the Application must have a list of keys or enum values that has all the possible binations, you will have to Query and go through them.

A long time has passed since this question, however, I will update the answers because currently there is a method more efficient than previously posted:

It's possible to use the function $objectToArray inside a $project stage to get every key of {k1:v1, k2:v2, ..., kn:vn} and its value in an array in the form:

[
    {"k":"k1", "v":"v1"},
    {"k":"k2", "v":"v2"},
    ...
    {"k":"kn", "v": "vn"}
]

Then you can use the $unwind stage and use another $project to get the nested properties.

collection.aggregate([
{"$project": {"colors_array": {"$objectToArray": "$colors"}},
{"$unwind": {"path": "$colors_array"}},
{"$project": {"data_colors": "$colors_array.v"}}
])

I think this could be enough to have an array like this one:

[
  {
    "prestock": 50,
    "instock": 60,
    "inactive": 0
  },
  {
    "prestock": 30,
    "instock": 0,
    "inactive": 0
  }
  ...
]

But, in case you want to maintain the name of the color, you could obviate the last stage of the aggregate pipeline.

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