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nomv

The nomv command converts a multivalue (array) field into a single-value string field by joining all array elements with newline characters (\n). This operation is performed in place, replacing the original field with its joined string representation.

Note: The field must be an array type. For scalar fields, use the array() function to convert the value into an array first.

Syntax

The nomv command has the following syntax:

nomv <field>

Parameters

The nomv command supports the following parameters.

Parameter Required/Optional Description
<field> Required The name of the field whose multivalue content should be converted to a single-value string.

Example: Convert a collected list to a single-value string

The following query collects all service names into an array. It then filters to include only services that reported errors and converts the array into a string:

source=otellogs
| where severityText = 'ERROR'
| stats list(`resource.attributes.service.name`) as affected_services by severityText
| nomv affected_services
| fields severityText, affected_services

The query returns the following results:

fetched rows / total rows = 1/1
+--------------+-------------------+
| severityText | affected_services |
|--------------+-------------------|
| ERROR        | payment           |
|              | checkout          |
|              | payment           |
|              | frontend-proxy    |
|              | recommendation    |
|              | product-catalog   |
|              | checkout          |
+--------------+-------------------+

Limitations

The nomv command has the following limitations:

  • The nomv command is only available when the Apache Calcite query engine is enabled.
  • The newline delimiter (\n) is fixed and cannot be customized. For custom delimiters, use the mvjoin function directly in an eval expression.
  • NULL values within the array are automatically filtered out and do not appear in the output.

Related commands

  • mvcombine -- Combines multiple rows into a single row with multivalue fields.
  • mvexpand -- Expands multivalue fields into separate rows.