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APPLIES TO:
MongoDB vCore
The $position
operator is used to specify the position in the array where a new element should be inserted. This operator is useful when you need to insert an element at a specific index in an array rather than appending it to the end.
Syntax
The basic syntax for using the $position
operator in an update command is as follows:
{
"$push": {
"<arrayField>": {
"$each": ["<value1>", "<value2>"],
"$position": <index>
}
}
}
Parameters
Description | |
---|---|
<arrayField> |
The field in the document that contains the array to be updated. |
<value1>, <value2>, ... |
The values to be inserted into the array. |
<index> |
The position at which the values should be inserted. |
Example
Let's understand the usage with sample json from stores
dataset.
{
"_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5",
"name": "Lakeshore Retail | DJ Equipment Stop - Port Cecile",
"location": { "lat": 60.1441, "lon": -141.5012 },
"staff": { "totalStaff": { "fullTime": 2, "partTime": 0 } },
"sales": {
"salesByCategory": [
{ "categoryName": "DJ Headphones", "totalSales": 35921 },
{ "categoryName": "DJ Cables", "totalSales": 1000 }
],
"fullSales": 3700
},
"promotionEvents": [
{
"eventName": "Bargain Blitz Days",
"promotionalDates": {
"startDate": { "Year": 2024, "Month": 3, "Day": 11 },
"endDate": { "Year": 2024, "Month": 2, "Day": 18 }
},
"discounts": [
{ "categoryName": "DJ Turntables", "discountPercentage": 18 },
{ "categoryName": "DJ Mixers", "discountPercentage": 15 }
]
},
{
"eventName": "Discount Delight Days",
"promotionalDates": {
"startDate": { "Year": 2024, "Month": 5, "Day": 11 },
"endDate": { "Year": 2024, "Month": 5, "Day": 18 }
}
}
],
"tag": [
"#ShopLocal",
"#FashionStore",
"#SeasonalSale",
"#FreeShipping",
"#MembershipDeals"
]
}
Example 1: Insert an element at specific index location in an array field
The example inserts the tag #NewArrival
at the second position (index 1) in the tag
array of a specific document.
db.stores.update(
{ "_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5" },
{ $push: { "tag": { $each: ["#NewArrival"], $position: 1 } } }
)
The example document updated tag
field has following values.
{
"_id": "7954bd5c-9ac2-4c10-bb7a-2b79bd0963c5",
"tag": [
"#ShopLocal",
"#NewArrival",
"#FashionStore",
"#SeasonalSale",
"#FreeShipping",
"#MembershipDeals"
]
}
Related content
- Review options for Migrating from MongoDB to Azure Cosmos DB for MongoDB (vCore)
- Read more about Feature compatibility with MongoDB