how to retrieve selected array object in mongodb

Question

I am having mongodb data like this

{
    "_id" : ObjectId("58eb32fb58bbf720a80daf6f"),
    "RoleName" : "Admin",
    "UIList" : [ 
        {
            "UiName" : "ManageRole",
            "View" : true,
            "Edit" : false,
            "_id" : ObjectId("58eb32fb58bbf720a80daf79")
        }, 
        {
            "UiName" : "ManageBuildings",
            "View" : false,
            "Edit" : false,
            "_id" : ObjectId("58eb32fb58bbf720a80daf78")
        }, 
        {
            "UiName" : "ManageFacility",
            "View" : true,
            "Edit" : false,
            "_id" : ObjectId("58eb32fb58bbf720a80daf77")
        }
    ],
    "__v" : 0,
    "Description" : "Full Control",
    "IsActive" : true
}

I want to retrieve only View:true in UIList under UiName:"ManageFacility" 's how to retrieve that.

I tried to get the data following this query but it retrieve all UIList Under Uiname:,View,Edit value.

db.getCollection("manage_roles_news").find(
    { _id:ObjectId("58eb32fb58bbf720a80daf6f")},
    {UIList: {$elemMatch: {UiName: "ManageFacility"}}});

How to retrieve that only view in UIlist under Uiname:"ManageFacility"

can anyone tell me

Try db.getCollection("manage_roles_news").find( { _id:ObjectId("58eb32fb58bbf720a80daf6f")}, {UIList: {$elemMatch: {UiName: "ManageFacility", View:true}}}); — s7vr
– s7vr, Commented Apr 11, 2017 at 13:59
Hi, @Veeram this query also return all the managefacility column — Vinoth
– Vinoth, Commented Apr 11, 2017 at 14:00

s7vr · Accepted Answer · 2017-04-12 09:38:31Z

1

I don't think there is way to project individual fields from positional/elemMatch projection. It always resolves to array element.

You can try below aggregation to project field. The below query uses $filter operator to find the matching array values which is piped to $arrayAtElem to return the first element (0) and pass the matching document to $let operator and followed by picking the View property.

db.getCollection("manage_roles_news").aggregate(
  { $match: { _id: ObjectId("58eb32fb58bbf720a80daf6f") } }, 
  { $project: { 
      _id:0,
      View: 
      { $let: { 
            vars: { 
              mElement: { 
                $arrayElemAt: [{
                            $filter: {
                                input: "$UIList",
                                as: "fElement",
                                cond: {
                                    $eq: ["$$fElement.UiName", "ManageFacility"]
                                }
                            }
                        }, 0]
                    }
                },
            in: {$cond:["$$mElement.View", 1, 0]}
            }
        }
    }
})

edited Apr 12, 2017 at 9:38

answered Apr 11, 2017 at 14:31

s7vr

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7 Comments

s7vr Over a year ago

1. Add _id:0 to exclude _id in the $project stage. 2 Replace "$$mElement.View" with {$cond: [ "$$mElement.View", 1, 0 ] }

Vinoth Over a year ago

can post this in another answer

s7vr Over a year ago

Sorry. I didn't understand you. Do you want me to update answer with the previous comment changes ?

Vinoth Over a year ago

now my requirement is: i want the count of table. i will give id value:"ObjectId("58eb32fb58bbf720a80daf6f")", UiName:"ManageFacilty",and View:"true". If the three conditions are satisfies return 1 or else. 0

Vinoth Over a year ago

db.getCollection("manage_roles_news").find( { _id:ObjectId("58eb32fb58bbf720a80daf6f")}, {UIList: {$elemMatch: {UiName: "ManageFacility", View:true}}});

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