Present in input array

Question

We have a stocks collection:

stocks:

{"_id" : ObjectId("xxx"),"scrip" : "xxxxx2" }
{"_id" : ObjectId("xxy"),"scrip" : "xxxxx3" }
{"_id" : ObjectId("xyy"),"scrip" : "..." }

Given an input array of scrips [xxxxx7,xxxxx2,xxxxx3,xxxxx8],we need to return an array of the scrips not present in the stocks collection.
So the expected output is :

[xxxxx7,xxxxx8]

Is there a way to achieve this using Filter.expr and $setIsSubset(or any other alternative).
Not able to get an example of the same.
Help is appreciated

You could try db.stocks.find({ '$expr': { '$not': { '$in: [ "$scripid" , inputArray ] } } }).toArray().map(doc => doc.scripid)? — chridam
– chridam, Commented Aug 16, 2019 at 14:11
Thanks.But what is the equivalent using java driver aggregate.We are using driver 3.5+ — IUnknown
– IUnknown, Commented Aug 16, 2019 at 16:11

whoami - fakeFaceTrueSoul · Accepted Answer · 2019-08-16 16:25:33Z

1

Assuming data in collection :

stocks:

{"scripid" : "xxxxx2" }
{"scripid" : "xxxxx3" }
{"scripid" : "xxxxx4" }

So if you need to get the list of elements from Input Array which are not in scripid of stocks collection, but not the list of elements from stocks collection which are not in input array, then use this:

db.stocks.aggregate([  {
             $group :{_id : null, scripids: {$push : '$scripid'}}
           },{ "$project": { _id:0 , "inputArrayNINscripts": { "$setDifference": [ ['xxxxx7','xxxxx2','xxxxx3','xxxxx8'] , "$scripids" ] } } } ])

Output:

{
    "inputArrayNINscripts" : [ 
        "xxxxx7", 
        "xxxxx8"
    ]
}

Else if you need list of elements(scripid's) from stocks scripid which aren't in passed [xxxxx7,xxxxx2,xxxxx3,xxxxx8] then, as suggested by @Caconde try this :

db.stocks.find({
    "scripid": {"$nin": ["xxxxx7","xxxxx2","xxxxx3","xxxxx8"]} 
}).toArray().map(scriptsNINArray => scriptsNINArray.scripid)

Output:

/* 1 */
[
    "xxxxx4"
]

Add-ons:

As requested for java code, Please check these references:

mongoDB-java-driver Aggregation , SO link to java aggregation example

edited Aug 16, 2019 at 16:25

answered Aug 16, 2019 at 15:32

whoami - fakeFaceTrueSoul

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2 Comments

IUnknown Over a year ago

Could not find the setDifference function for java driver though

whoami - fakeFaceTrueSoul Over a year ago

@IUnknown : not sure about java driver, but does the query work in DB ? Please put on a tag for JAVA or raise a new question, meanwhile just found something here in SO, Please check this for java : stackoverflow.com/questions/42351139/…

Caconde · Accepted Answer · 2019-08-16 15:06:01Z

0

You can achieve the expected result with MongoDB's Not In operator $nin and mapping the result to an array:

db.stocks.find({
    "scripid": {"$nin": ["xxxxx7","xxxxx2","xxxxx3","xxxxx8"]} 
}).toArray().map(stock => stock.scripid)

answered Aug 16, 2019 at 15:06

Caconde

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