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Aggregation Operations

Reference

Operators

$toInt (aggregation)

Definition

$toInt

Converts a value to an integer. If the value cannot be converted to an integer, $toInt errors. If the value is null or missing, $toInt returns null.

$toInt has the following syntax:

{
   $toInt: <expression>
}

The $toInt takes any valid expression.

The $toInt is a shorthand for the following $convert expression:

{ $convert: { input: <expression>, to: "int" } }

Behavior

The following table lists the input types that can be converted to an integer:

Input Type	Behavior
Boolean	Returns `0` for `false`. Returns `1` for `true`.
Double	Returns truncated value. The truncated double value must fall within the minimum and maximum value for an integer. You cannot convert a double value whose truncated value is less than the minimum integer value or is greater than the maximum integer value.
Decimal	Returns truncated value. The truncated decimal value must fall within the minimum and maximum value for an integer. You cannot convert a decimal value whose truncated value is less than the minimum integer value or is greater than the maximum integer value.
Integer	No-op. Returns the integer value.
Long	Returns the long value as an integer. The long value must fall within the minimum and maximum value for an integer. You cannot convert a long value that is less than the minimum integer value or is greater than the maximum integer value.
String	Returns the numerical value of the string as an integer. The string value must be a base ₁₀ integer; e.g. `"-5"`, `"123456"`). You cannot convert a string value of a float or decimal or non-base ₁₀ number (e.g. `"-5.0"`, `"0x6400"`)

The following table lists some conversion to integer examples:

Example	Results
`$toInt: true`	1
`$toInt: false`	0
`$toInt: 1.99999`	1
`$toInt: NumberDecimal("5.5000")`	5
`$toInt: NumberDecimal("9223372036000.000")`	Error
`$toInt: NumberLong("5000")`	5000
`$toInt: NumberLong("922337203600")`	Error
`$toInt: "-2"`	-2
`$toInt: "2.5"`	Error
`$toInt: null`	null

Example

Create a collection orders with the following documents:

db.orders.insertMany( [
   { _id: 1, item: "apple", qty: "5", price: 10 },
   { _id: 2, item: "pie", qty: "10", price: NumberDecimal("20.0") },
   { _id: 3, item: "ice cream", qty: "2", price: "4.99" },
   { _id: 4, item: "almonds" ,  qty: "5", price: 5 }
] )

The following aggregation operation:

converts qty to an integer,
converts price to a decimal,
calculates the total price:

// Define stage to add convertedPrice and convertedQty fields with the converted price and qty values
priceQtyConversionStage = {
   $addFields: {
      convertedPrice: { $toDecimal: "$price" },
      convertedQty: { $toInt: "$qty" },
   }
};
// Define stage to calculate total price by multiplying convertedPrice and convertedQty fields
totalPriceCalculationStage = {
   $project: { item: 1, totalPrice: { $multiply: [ "$convertedPrice", "$convertedQty" ] } }
};
db.orders.aggregate( [
   priceQtyConversionStage,
   totalPriceCalculationStage
] )

The operation returns the following documents:

{ _id: 1, item: 'apple', totalPrice: Decimal128("50") },
{ _id: 2, item: 'pie', totalPrice: Decimal128("200.0") },
{ _id: 3, item: 'ice cream', totalPrice: Decimal128("9.98") },
{ _id: 4, item: 'almonds', totalPrice: Decimal128("25") }

Note

If the conversion operation encounters an error, the aggregation operation stops and throws an error. To override this behavior, use $convert instead.

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