The mv-expand operator expands dynamic arrays and property bags into multiple rows. Each element of the array or each property of the bag becomes its own row, while other columns are duplicated.
You use mv-expand when you want to analyze or filter individual values inside arrays or objects. This is especially useful when working with logs that include lists of values, OpenTelemetry traces that contain arrays of spans, or security events that group multiple attributes into one field.
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.
In Splunk SPL, the mvexpand command expands multi-value fields into separate events. The APL mv-expand operator works in a very similar way, splitting array values into individual rows. The main difference is that APL explicitly works with dynamic arrays or property bags, while Splunk handles multi-value fields implicitly.
['sample-http-logs']
| mv-expand uriIn ANSI SQL, you use CROSS JOIN UNNEST or CROSS APPLY to flatten arrays into rows. In APL, mv-expand provides a simpler and more direct way to achieve the same result.
['sample-http-logs']
| mv-expand uriUsage
Syntax
mv-expand [kind=(bag|array)] [with_itemindex=IndexFieldName] FieldName [to typeof(Typename)] [limit Rowlimit]Parameters
| Parameter | Description |
|---|---|
kind |
Optional. Specifies whether the column is a bag (object) or an array. Defaults to array. |
with_itemindex=IndexFieldName |
Optional. Outputs an additional column with the zero-based index of the expanded item. |
FieldName |
Required. The name of the column that contains an array or object to expand. |
to typeof(Typename) |
Optional. Converts each expanded element to the specified type. |
limit Rowlimit |
Optional. Limits the number of expanded rows per record. |
Returns
The operator returns a table where each element of the expanded array or each property of the expanded object is placed in its own row. Other columns are duplicated for each expanded row.
Use case example
When analyzing logs, some values can be stored as arrays. You can use mv-expand to expand them into individual rows for easier filtering.
Query
['sample-http-logs']
| limit 100
| mv-expand territories
| summarize count = count() by territory_name = tostring(territories)Output
| territory_name | count |
|---|---|
| United States | 67 |
| India | 22 |
| Japan | 12 |
This query expands the territories array into rows and counts the most frequent territories.