make_list_if aggregation function in APL creates a list of values from a given field, conditioned on a Boolean expression. This function is useful when you need to gather values from a column that meet specific criteria into a single array. By using make_list_if, you can aggregate data based on dynamic conditions, making it easier to perform detailed analysis.
This aggregation is ideal in scenarios where filtering at the aggregation level is required, such as gathering only the successful requests or collecting trace spans of a specific service in OpenTelemetry data. It’s particularly useful when analyzing logs, tracing information, or security events, where conditional aggregation is essential for understanding trends or identifying issues.
For users of other query languages
If you come from other query languages, this section explains how to adjust your existing queries to achieve the same results in APL.Splunk SPL users
Splunk SPL users
In Splunk, you would typically use the
eval and stats commands to create conditional lists. In APL, the make_list_if function serves a similar purpose by allowing you to aggregate data into a list based on a condition.ANSI SQL users
ANSI SQL users
In ANSI SQL, conditional aggregation often involves the use of
CASE statements combined with aggregation functions such as ARRAY_AGG. In APL, make_list_if directly applies a condition to the aggregation.Usage
Syntax
Parameters
expression: The field or expression whose values will be included in the list.condition: A Boolean condition that determines which values fromexpressionare included in the result.
Returns
The function returns an array containing all values fromexpression that meet the specified condition.
Use case examples
In this example, we will gather a list of request durations for successful HTTP requests.QueryRun in PlaygroundOutput
This query aggregates request durations for HTTP requests that returned a status of ‘200’ for each user ID.
| id | req_duration_ms_list |
|---|---|
| 123 | [100, 150, 200] |
| 456 | [300, 350, 400] |
List of related aggregations
- make_list: Aggregates all values into a list without any conditions. Use
make_listwhen you don’t need to filter the values based on a condition. - countif: Counts the number of records that satisfy a specific condition. Use
countifwhen you need a count of occurrences rather than a list of values. - avgif: Calculates the average of values that meet a specified condition. Use
avgiffor numerical aggregations where you want a conditional average instead of a list.