top

This page explains how to use the top operator function in APL.

The top operator in Axiom Processing Language (APL) allows you to retrieve the top N rows from a dataset based on specified criteria. It’s particularly useful when you need to analyze the highest values in large datasets or want to quickly identify trends, such as the highest request durations in logs or top error occurrences in traces. You can apply it in scenarios like log analysis, security investigations, or tracing system performance.

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 top operator in APL is similar to top in Splunk SPL but allows greater flexibility in specifying multiple sorting criteria.

Splunk example

index="sample_http_logs" | top limit=5 req_duration_ms

ANSI SQL users

In ANSI SQL, the TOP operator is used with an ORDER BY clause to limit the number of rows. In APL, the syntax is similar but uses top in a pipeline and specifies the ordering criteria directly.

SQL example

SELECT TOP 5 req_duration_ms FROM sample_http_logs ORDER BY req_duration_ms DESC

Usage

Syntax

| top N by Expression [asc | desc]

Parameters

• N: The number of rows to return.
• Expression: A scalar expression used for sorting. The type of the values must be numeric, date, time, or string.
• [asc | desc]: Optional. Use to sort in ascending or descending order. The default is descending.

Returns

The top operator returns the top N rows from the dataset based on the specified sorting criteria.

Use case examples

Log analysis

The top operator helps you find the HTTP requests with the longest durations.

Query

['sample-http-logs']
| top 5 by req_duration_ms

Run in Playground

Output

_time	req_duration_ms	id	status	uri	method	geo.city	geo.country
2024-10-01 10:12:34	5000	123	200	/api/get-data	GET	New York	US
2024-10-01 11:14:20	4900	124	200	/api/post-data	POST	Chicago	US
2024-10-01 12:15:45	4800	125	200	/api/update-item	PUT	London	UK

This query returns the top 5 HTTP requests that took the longest time to process.

List of related operators

• order: Use when you need full control over row ordering without limiting the number of results.
• summarize: Useful when aggregating data over fields and obtaining summarized results.
• take: Returns the first N rows without sorting. Use when ordering isn’t necessary.