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.
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
The top operator helps you find the HTTP requests with the longest durations.
Query
['sample-http-logs']
| top 5 by req_duration_msOutput
| _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.
The top operator is useful for identifying the spans with the longest duration in distributed tracing systems.
Query
['otel-demo-traces']
| top 5 by durationOutput
| _time | duration | span_id | trace_id | service.name | kind | status_code |
|---|---|---|---|---|---|---|
| 2024-10-01 10:12:34 | 300ms | span123 | trace456 | frontend | server | 200 |
| 2024-10-01 10:13:20 | 290ms | span124 | trace457 | cartservice | client | 200 |
| 2024-10-01 10:15:45 | 280ms | span125 | trace458 | checkoutservice | server | 500 |
This query returns the top 5 spans with the longest durations from the OpenTelemetry traces.
The top operator is useful for identifying the most frequent HTTP status codes in security logs.
Query
['sample-http-logs']
| summarize count() by status
| top 3 by count_Output
| status | count_ |
|---|---|
| 200 | 500 |
| 404 | 50 |
| 500 | 20 |
This query shows the top 3 most common HTTP status codes in security logs.
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.