array_slice

This page explains how to use the array_slice function in APL.

The array_slice function in APL extracts a subset of elements from an array, based on specified start and end indices. This function is useful when you want to analyze or transform a portion of data within arrays, such as trimming logs, filtering specific events, or working with trace data in OpenTelemetry logs.

Usage

Syntax

array_slice(array, start, end)

Parameters

Parameter	Description
`array`	The input array to slice.
`start`	The starting index of the slice (inclusive). If negative, it’s counted from the end of the array.
`end`	The ending index of the slice (exclusive). If negative, it’s counted from the end of the array.

Returns

An array containing the elements from the specified slice. If the indices are out of bounds, it adjusts to return valid elements without error.

Use case example

Filter spans from trace data to analyze a specific range of events.

Query

['otel-demo-traces']
| where array_length(events) > 4
| extend sliced_events = array_slice(events, -3, -1)

Run in Playground

Output

[
  {
    "timestamp": 1734001336443987200,
    "attributes": null,
    "name": "prepared"
  },
  {
    "attributes": {
      "feature_flag.provider_name": "flagd",
      "feature_flag.variant": "off",
      "feature_flag.key": "paymentServiceUnreachable"
    },
    "name": "feature_flag",
    "timestamp": 1734001336444001800
  },
  {
    "name": "charged",
    "timestamp": 1734001336445970200,
    "attributes": {
      "custom": {
        "app.payment.transaction.id": "49567406-21f4-41aa-bab2-69911c055753"
      }
    }
  },
  {
    "name": "shipped",
    "timestamp": 1734001336446488600,
    "attributes": {
      "custom": {
        "app.shipping.tracking.id": "9a3b7a5c-aa41-4033-917f-50cb7360a2a4"
      }
    }
  },
  {
    "attributes": {
      "feature_flag.variant": "off",
      "feature_flag.key": "kafkaQueueProblems",
      "feature_flag.provider_name": "flagd"
    },
    "name": "feature_flag",
    "timestamp": 1734001336461096700
  }
]

[
  {
    "name": "charged",
    "timestamp": 1734001336445970200,
    "attributes": {
      "custom": {
        "app.payment.transaction.id": "49567406-21f4-41aa-bab2-69911c055753"
      }
    }
  },
  {
    "name": "shipped",
    "timestamp": 1734001336446488600,
    "attributes": {
      "custom": {
        "app.shipping.tracking.id": "9a3b7a5c-aa41-4033-917f-50cb7360a2a4"
      }
    }
  }
]

Slices the last three events from the events array, excluding the final one.

array_concat: Combines multiple arrays.
array_reverse: Reverses the order of array elements.
array_shift_right: Shifts array elements to the right.