[PR] perf(arrow/ipc): slice already-zero-based offset buffers [arrow-go]

["fallintoplace (via GitHub)" <gi...@apache.org>]

fallintoplace opened a new pull request, #1191:
URL: https://github.com/apache/arrow-go/pull/1191

   ### Rationale for this change
   
   IPC currently allocates a new offsets buffer whenever a variable-length array has unused trailing offsets. For a prefix slice, the first logical offset is already zero, so the loop only copies every offset and subtracts zero.
   
   Arrow C++ handles this case by slicing the existing offsets buffer.
   
   ### What changes are included in this PR?
   
   - Read the first logical offset instead of treating every sliced array as needing rebasing.
   - Rebase only when that offset is non-zero.
   - Use `memory.SliceBuffer` when the required offsets are already zero-based.
   - Add coverage for int32 and int64 offsets, middle slices, and slices with a non-zero array offset whose first logical value offset is zero.
   
   The benchmark uses a 524,288-value slice from a 1,048,576-value backing array. Medians from 6 runs on an Apple M1 Pro were:
   
   | prefix slice | main | this PR |
   |---|---:|---:|
   | int32 time/op | 238 us | 40.7 ns |
   | int32 B/op | 2,106,000 | 80 |
   | int64 time/op | 283 us | 40.7 ns |
   | int64 B/op | 4,203,153 | 80 |
   | allocs/op | 8 | 1 |
   
   Unsliced buffers remain allocation-free. Middle slices that need rebasing are unchanged.
   
   ### Are these changes tested?
   
   - `go test ./arrow/ipc -count=1`
   - `go test ./arrow/... -count=1`
   - `go test ./arrow/ipc -run "^$" -bench "^BenchmarkGetZeroBasedValueOffsets$" -benchmem -count=6`
   
   ### Are there any user-facing changes?
   
   No. The IPC output and public API are unchanged.


-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: github-unsubscribe@arrow.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org

Re: [PR] perf(arrow/ipc): slice already-zero-based offset buffers [arrow-go]

["zeroshade (via GitHub)" <gi...@apache.org>]

zeroshade merged PR #1191:
URL: https://github.com/apache/arrow-go/pull/1191


-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: github-unsubscribe@arrow.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org