$replaceWith

05/09/2025

The $replaceWith aggregation stage operator is used to replace the input document with the specified document. The $replaceWith operator transforms documents from one structure to another or replaces them entirely with new fields and values.

Syntax

{
  "$replaceWith": <newDocument>
}

Parameters

Parameter	Description
`newDocument`	The new document to replace the original document

Examples

Consider this sample document from the stores collection in the StoreData database.

{
    "_id": "0fcc0bf0-ed18-4ab8-b558-9848e18058f4",
    "name": "First Up Consultants | Beverage Shop - Satterfieldmouth",
    "location": {
        "lat": -89.2384,
        "lon": -46.4012
    },
    "staff": {
        "totalStaff": {
            "fullTime": 8,
            "partTime": 20
        }
    },
    "sales": {
        "totalSales": 75670,
        "salesByCategory": [
            {
                "categoryName": "Wine Accessories",
                "totalSales": 34440
            },
            {
                "categoryName": "Bitters",
                "totalSales": 39496
            },
            {
                "categoryName": "Rum",
                "totalSales": 1734
            }
        ]
    },
    "promotionEvents": [
        {
            "eventName": "Unbeatable Bargain Bash",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 6,
                    "Day": 23
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 7,
                    "Day": 2
                }
            },
            "discounts": [
                {
                    "categoryName": "Whiskey",
                    "discountPercentage": 7
                },
                {
                    "categoryName": "Bitters",
                    "discountPercentage": 15
                },
                {
                    "categoryName": "Brandy",
                    "discountPercentage": 8
                },
                {
                    "categoryName": "Sports Drinks",
                    "discountPercentage": 22
                },
                {
                    "categoryName": "Vodka",
                    "discountPercentage": 19
                }
            ]
        },
        {
            "eventName": "Steal of a Deal Days",
            "promotionalDates": {
                "startDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 21
                },
                "endDate": {
                    "Year": 2024,
                    "Month": 9,
                    "Day": 29
                }
            },
            "discounts": [
                {
                    "categoryName": "Organic Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "White Wine",
                    "discountPercentage": 20
                },
                {
                    "categoryName": "Sparkling Wine",
                    "discountPercentage": 19
                },
                {
                    "categoryName": "Whiskey",
                    "discountPercentage": 17
                },
                {
                    "categoryName": "Vodka",
                    "discountPercentage": 23
                }
            ]
        }
    ]
}

Example 1 - Return a document that replaces the contents of the original document with a subset of items

First, match a specific document to replace by the _id field and replace the contents of the document with the specified fields.

db.stores.aggregate([{ "$match": { "_id": "bda56164-954d-4f47-a230-ecf64b317b43" } }, { "$replaceWith": { "_id": "$_id", "name": "$name", "sales": "$sales.totalSales" } }])

This returns the following result:

{
    "_id": "bda56164-954d-4f47-a230-ecf64b317b43",
    "name": "Boulder Innovations | Home Security Place - Ankundingburgh",
    "sales": 37015
}

Example 2 - Return a document that replaces the contents of the original document after aggregating specified fields

db.stores.aggregate([{ "$match": { "_id": "bda56164-954d-4f47-a230-ecf64b317b43" } }, { "$replaceWith": { "_id": "$_id", "name": "$name", "totalStaff": {"$add": ["$staff.totalStaff.fullTime", "$staff.totalStaff.partTime"]}}}])