Projection of array elements using MongoDB

Question

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.

JohnnyHK · Accepted Answer · 2013-02-12 16:51:46Z

3

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})

answered Feb 12, 2013 at 16:51

JohnnyHK

313k70 gold badges632 silver badges479 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Yannis Over a year ago

I m sure I tried that before I posted my question. In any case it works exactly as I wanted. Thanks a lot.

Collectives™ on Stack Overflow

Projection of array elements using MongoDB

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related