c# - Unwind array and return the last element matching condition -


say have document structure looks like

[     {          _id:1,         logs : [             { time: 123, x: 24 },             { time: 212, x: 13 },             { time: 325, x: 34 }         ]     },     {          _id:2,         logs : [             { time: 63, x: 19 },             { time: 112, x: 25 },             { time: 205, x: 15 }         ]     } ]

what i'm trying value of x time < n , _id = y

so example, if y=2, , n=115 want 25 return.

given time < 115 , greatest time matching filter in array?

i'm going in c#, convert shell syntax if can help?

thanks

edit:

so question i'm asking is... $elemmatch return document if finds 1 match, $elemmatch on time<115 , _id=2 return second document. if project array, 3 logs sub docs.

i'm therefore assuming need use aggregation filter projected array?

the following aggregation desired results:

db.collection.aggregate([    {      "$match": {"_id": y, "logs.time": {"$lt": n} }    },    {      "$unwind": "$logs"    },     {      "$match": {"logs.time": {"$lt": n} }    },    {      "$group": {          "_id": "$_id",          "x": { "$max": "$logs.x"  }      }    },    {      "$project": {          "_id": 0,          "x": 1      }    } ])

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