CODEWITHSUNDEEP
node.jsmongodb
Yannis
Yannis

Reputation: 6157

Projection of array elements using MongoDB

I have the following json document:

{
    "Section": {
        "Name": "Section 1",
        "Description": "Section 1 information",
        "Icon": "test.png"
    },
    "Data": [{
        "Name": "Firstname",
        "Desc": "Users first name",
        "Type": "Text"
    }, {
        "Name": "Lastname",
        "Desc": "Users last name",
        "Type": "Text"
    }]
} {
    "Section": {
        "Name": "Section 2",
        "Description": "Section 2 information",
        "Icon": "test.png"
    },
    "Data": [{
        "Name": "Section 2 Item",
        "Desc": "Section 2 Desc",
        "Type": "Text"
    }]
}

I wanted to ask if there is any way to project items based on Data.Name. Like project everything with Data.Name in ['Firstname', 'Section 2 Item'] including the Section object. So the result should be:

{
    "Section": {
        "Name": "Section 1",
        "Description": "Section 1 information",
        "Icon": "test.png"
    },
    "Data": [{
        "Name": "Firstname",
        "Desc": "Users first name",
        "Type": "Text"
    }]
} {
    "Section": {
        "Name": "Section 2",
        "Description": "Section 2 information",
        "Icon": "test.png"
    },
    "Data": [{
        "Name": "Section 2 Item",
        "Desc": "Section 2 Desc",
        "Type": "Text"
    }]
}

Not sure if this is possible.

Thanks in advance.

Upvotes: 0

Views: 1782

Answers (1)

JohnnyHK
JohnnyHK

Reputation: 311835

You can do this with the $ positional projection operator which identifies the index of the array element matched in the query object:

db.test.find(
    {'Data.Name': {$in: ["Firstname", "Section 2 Item"]}}, 
    {Section: 1, 'Data.$': 1})

Upvotes: 3

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