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.

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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

array_slice(array, start, end)

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Parameters

ParameterDescription
arrayThe input array to slice.
startThe starting index of the slice (inclusive). If negative, it is counted from the end of the array.
endThe ending index of the slice (exclusive). If negative, it is counted from the end of the array.

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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.

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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

events
[
  {
    "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
  }
]
sliced_events
[
  {
    "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.

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array_shift_rightarray_split