$bsonSize
The $bsonSize operator returns the size of a document in bytes when encoded as BSON.
$bsonSize
The $bsonSize operator is used to return the size of a document in bytes when encoded as BSON. It's useful for understanding the storage requirements of documents within your collections. The operator can be used within aggregation pipelines to calculate the size of documents and is helpful for optimizing storage and understanding performance implications.
Syntax
{
$bsonSize: <expression>
}Parameters
| Parameter | Description |
|---|---|
<expression> | Any valid expression that resolves to a document whose BSON size you want to calculate. |
Examples
Consider this sample document from the stores collection.
{
"_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: Calculate the total BSON-encoded size of a document in bytes using $bsonSize
This query calculates the BSON size of the document.
db.stores.aggregate([
{
$project: {
_id: 1,
name: 1,
documentSize: {
$bsonSize: "$$ROOT" //pass the whole document
}
}
},
// Limit the result to the first 3 documents
{ $limit: 3 }
])The first three results returned by this query are:
[
{
"_id": "a715ab0f-4c6e-4e9d-a812-f2fab11ce0b6",
"name": "Lakeshore Retail | Holiday Supply Hub - Marvinfort",
"documentSize": 2226
},
{
"_id": "923d2228-6a28-4856-ac9d-77c39eaf1800",
"name": "Lakeshore Retail | Home Decor Hub - Franciscoton",
"documentSize": 1365
},
{
"_id": "7e53ca0f-6e24-4177-966c-fe62a11e9af5",
"name": "Contoso, Ltd. | Office Supply Deals - South Shana",
"documentSize": 1882
}
]