Add OTTL delete function

[alexcams]

Description

Added new ottl function delete_index(target, startIndex, Optional[endIndex]

The delete_index function removes elements from a slice. It deletes elements in the range [startIndex, endIndex) (startIndex inclusive, endIndex exclusive). If endIndex is not provided, only the element at target[startIndex] is deleted. If startIndex equals endIndex, no changes are applied to the target, following the behavior of Go's slices.Delete(s, i, j) function.

It accepts any OTTL array type, including arrays with different type of data.
Implemented this as a function modifying target rather than converter returning merged arrays
This implementation doesn't delete duplicate values, could be added in the future or implemented as a separated function.

Note Following golang Slices.Delete() function behavior, any case where index out of bouds ( i < 0 || (i+len) > size(slice)) will return an error.

Link to tracking issue

Closes #43098

Testing

Added unit tests with intended behavior.
Tested manually with following config:

receivers:
  filelog:
    include: [ test.log ]
    start_at: beginning

exporters:
  debug:
    verbosity: detailed
    sampling_initial: 10000
    sampling_thereafter: 10000

processors:
  transform:
    error_mode: ignore
    log_statements:
      - context: log
        statements: 
          - set(attributes["test"], [[1, 2, 3, 4]]) # init slice with nested slice
          - append(attributes["test"], values = ["val", 1, true, 3.14, "foo", "foo", 2, false, 6.28]) # append multiple values
          - set(attributes["test_copy"], attributes["test"]) # make a copy 
          - delete_index(attributes["test"], 1) # delete "val"
          - delete_index(attributes["test"], Len(attributes["test"]) - 1) # delete last element (6,28)
          - delete_index(attributes["test"], Index(attributes["test"], "foo")) # delete "foo" first instance
          - delete_index(attributes["test_copy"], 0, endIndex=4) # delete first 4 elements from copy

service:
  telemetry:
    metrics:
      level: none
  pipelines:
    logs:
      receivers: [filelog]
      processors: [transform]
      exporters:
        - debug

Output:

Body: Str(2025-11-05 10:00:00 INFO Test log message)
Attributes:
     -> log.file.name: Str(test.log)
     -> test: Slice([[1,2,3,4],1,true,3.14,"foo",2,false])
     -> test_copy: Slice([3.14,"foo","foo",2,false,6.28])

Documentation

Updated README.md

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: evan-bradley / name: Evan Bradley (85ba8d6)

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[alexcams]

Last commit updates the first implemented algorithm to a new one that avoids the use of AsRaw() and FromRaw() functions, both of cost O(N). Instead it is replaces by a single loop O(N) and preallocating memory for the result slice.
Here's a comparative between both algorithms showing that the second one reduces time and memory spent for different scenarios by 50% (at least).

[edmocosta]

@TylerHelmuth @evan-bradley @bogdandrutu Please take a look once you get a chance. Thanks!

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 14 days.

[evan-bradley]

Sorry for the delay @alexcams. We are determining how we want to name this function, and there are extra considerations involved in which name we ultimately go with. @edmocosta or I will give you an update as soon as we are able.

[alexcams]

@evan-bradley Don't worry :) Naming can be challenging sometimes and I think delete is too generic for a function that just deletes elements from slices. I'm here for any doubt!

[edmocosta]

Hi @alexcams! Just to give you some context, we're considering a few renaming/standardization for slices/maps functions, but to not delay this PR that much, we agreed on the delete_index name. It's a bit more specific, and we can tackle the standardization later with the other functions. Thanks!

[alexcams]

/rerun

[evan-bradley]

Thanks @alexcams!

[otelbot]

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