pack_dictionary

Use the pack_dictionary function in APL to construct a dynamic property bag (dictionary) from a list of keys and values. The resulting dictionary maps each specified key to its corresponding value and allows you to store key-value pairs in a single column for downstream operations like serialization, custom grouping, or structured export.

pack_dictionary is especially useful when you want to:

• Create flexible data structures for export or transformation.
• Group dynamic sets of key-value metrics or attributes into a single column.
• Combine multiple scalar fields into a single dictionary for post-processing or output.

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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.

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Usage

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Syntax

pack_dictionary(key1, value1, key2, value2, ...)

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Parameters

• The number of arguments must be even.
• Keys must be constant strings.
• Values can be any scalar type.

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Returns

A dynamic object that represents a dictionary where each key maps to its associated value.

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Use case examples

['sample-http-logs']
| extend request_info = pack_dictionary(
    'method', method,
    'uri', uri,
    'status', status,
    'duration', req_duration_ms
)
| project _time, id, request_info

['sample-http-logs']
| extend request_info = pack_dictionary(
    'method', method,
    'uri', uri,
    'status', status,
    'duration', req_duration_ms
)
| project _time, id, request_info

['otel-demo-traces']
| extend trace_metadata = pack_dictionary(
    'trace_id', trace_id,
    'span_id', span_id,
    'service', ['service.name'],
    'kind', kind,
    'status_code', status_code
)
| project _time, duration, trace_metadata

['sample-http-logs']
| extend geo_info = pack_dictionary(
    'city', ['geo.city'],
    'country', ['geo.country']
)
| extend request_info = pack_dictionary(
    'method', method,
    'uri', uri,
    'status', status,
    'geo', geo_info
)
| project _time, id, request_info

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List of related functions

• pack_array: Use this to combine scalar values into an array. Use pack_array when you don’t need named keys and want positional data instead.
• bag_keys: Returns the list of keys in a dynamic dictionary. Use this to inspect or filter contents created by pack_dictionary.
• bag_pack: Expands a dictionary into multiple columns. Use it to revert the packing performed by pack_dictionary.