percentileif

This page explains how to use the percentileif aggregation function in APL.

The percentileif aggregation function calculates the percentile of a numeric column, conditional on a specified boolean predicate. This function is useful for filtering data dynamically and determining percentile values based only on relevant subsets of data.

You can use percentileif to gain insights in various scenarios, such as:

• Identifying response time percentiles for HTTP requests from specific regions.
• Calculating percentiles of span durations for specific service types in OpenTelemetry traces.
• Analyzing security events by percentile within defined risk categories.

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

The percentileif aggregation in APL works similarly to percentile combined with conditional filtering in SPL. However, APL integrates the condition directly into the aggregation for simplicity.

Splunk example

stats perc95(req_duration_ms) as p95 where geo.country="US"

ANSI SQL users

In SQL, you typically calculate percentiles using window functions or aggregate functions combined with a WHERE clause. APL simplifies this by embedding the condition directly in the percentileif aggregation.

SQL example

SELECT PERCENTILE_CONT(0.95) WITHIN GROUP (ORDER BY req_duration_ms)
FROM sample_http_logs
WHERE geo_country = 'US'

Usage

Syntax

summarize percentileif(Field, Percentile, Predicate)

Parameters

Parameter	Description
Field	The numeric field from which to calculate the percentile.
Percentile	A number between 0 and 100 that specifies the percentile to calculate.
Predicate	A Boolean expression that filters rows to include in the calculation.

Returns

The function returns a single numeric value representing the specified percentile of the Field for rows where the Predicate evaluates to true.

Use case examples

Log analysis

You can use percentileif to analyze request durations for specific HTTP methods.

Query

['sample-http-logs']
| summarize post_p90 = percentileif(req_duration_ms, 90, method == "POST"), get_p90 = percentileif(req_duration_ms, 90, method == "GET") by bin_auto(_time)

Run in Playground

Output

post_p90	get_p90
1.691 ms	1.453 ms

This query calculates the 90th percentile of request durations for HTTP POST and GET methods.

You can use percentileif to analyze request durations for specific HTTP methods.

Query

['sample-http-logs']
| summarize post_p90 = percentileif(req_duration_ms, 90, method == "POST"), get_p90 = percentileif(req_duration_ms, 90, method == "GET") by bin_auto(_time)

Run in Playground

Output

post_p90	get_p90
1.691 ms	1.453 ms

This query calculates the 90th percentile of request durations for HTTP POST and GET methods.

You can use percentileif to measure span durations for specific services and operation kinds.

Query

['otel-demo-traces']
| summarize percentileif(duration, 95, ['service.name'] == 'frontend' and kind == 'server')

Run in Playground

Output

Percentile95
1.2s

This query calculates the 95th percentile of span durations for server spans in the frontend service.

You can use percentileif to calculate response time percentiles for specific HTTP status codes.

Query

['sample-http-logs']
| summarize percentileif(req_duration_ms, 75, status == '404')

Run in Playground

Output

Percentile75
350

This query calculates the 75th percentile of request durations for HTTP 404 errors.

List of related aggregations

• percentile: Calculates the percentile for all rows without any filtering. Use percentile when you don’t need conditional filtering.
• avgif: Calculates the average of a numeric column based on a condition. Use avgif for mean calculations instead of percentiles.
• minif: Returns the minimum value of a numeric column where a condition is true. Use minif for identifying the lowest values within subsets.
• maxif: Returns the maximum value of a numeric column where a condition is true. Use maxif for identifying the highest values within subsets.
• sumif: Sums a numeric column based on a condition. Use sumif for conditional total calculations.