$compute

Functionality

Definition

The $compute endpoint allows you to perform calculations on attributes within a dataclass. This can be done on simple attributes or on properties of object attributes. The calculations are specified using various keywords.

tip

This is useful for obtaining statistical information such as sum, average, count, minimum, and maximum values for numerical attributes, and count, minimum, and maximum values for string attributes.

Keywords

The following keywords can be used with $compute to perform different calculations:

Keyword	Description
$all	A JSON object that defines all the functions for the attribute (average, count, min, max, and sum for numerical attributes, and count, min, and max for string attributes)
average	Get the average of a numerical attribute
count	Get the total number of entries in the collection or dataclass (must specify an attribute)
min	Get the minimum value of a numerical attribute or the lowest value of a string attribute
max	Get the maximum value of a numerical attribute or the highest value of a string attribute
sum	Get the sum of a numerical attribute

Syntax

To perform a calculation on an attribute, you use the following format:

GET /rest/{{dataClass}}/{{attribute}}?$compute={{keyword}}

If you want to perform a calculation on an object attribute, specify one of its properties:

GET /rest/{{dataClass}}/{{objectAttribute}}.{{property}}?$compute={{keyword}}

Detailed Behavior

Using $compute=$all

When using $compute=$all, the response includes all possible calculations for the attribute:

• For numerical attributes: count, sum, average, min, max

• For string attributes: count, min, max

• For date attributes:

Using Specific Keywords

You can specify a particular calculation by replacing $all with one of the specific keywords (average, count, min, max, sum). The response will then include only the result of the specified calculation.

Object Attributes

If you need to perform calculations on a property of an object attribute, you must specify the property in the request URL. The calculation will be performed on the specified property.

Combining with Other Parameters

The $compute parameter can be combined with other parameters:

• $filter: Narrow down the data set before computing values.

• $orderby: Sort the data before computing values.

• $top/$limit and $skip: Limit the number of records and skip a certain number of records.

• $expand: Include related data in the computation.

• $attributes: Specify which attributes to include in the response with computed values.

• $method=entityset: Create an entity set based on computed results and save it in the server's cache.

Use Cases

Get All Computations for a Numerical Attribute

Request:

GET /rest/Payments?$attributes=Amount&$compute=$all

Response:

{
    "Amount": {
        "count": 20,
        "sum": 12,
        "average": 0.6,
        "min": -128,
        "max": 124
    }
}

Get All Computations for a String Attribute

Request:

GET /rest/Users?$attributes=Name&$compute=$all

Response:

{
    "Name": {
        "count": 11,
        "min": "Harry",
        "max": "user8"
    }
}

Get All Computations for a Date Attribute

Request:

GET /rest/Payments?$attributes=PaymentDate&$compute=$all

Response:

{
    "PaymentDate": {
        "count": 20,
        "min": "2024-01-01T00:00:00.000Z",
        "max": "2024-01-29T00:00:00.000Z"
    }
}

Get Sum of a Numerical Attribute

Request:

GET /rest/Payments?$attributes=Amount&$compute=sum

Response:

12

Get Count of a Numerical Attribute

Request:

GET /rest/Payments?$attributes=Amount&$compute=count

Response:

20

Best Practices

• Specify Only Necessary Calculations: Limit the calculations to those necessary for your application to optimize performance and reduce payload size.

• Combine with Other Query Parameters: Use other query parameters ($filter, $orderby) to refine your data retrieval and calculations.

• Handle Errors Gracefully: Implement proper error handling to manage cases where the calculations cannot be performed or data cannot be retrieved.