fallintoplace opened a new pull request, #1253:
URL: https://github.com/apache/arrow-go/pull/1253

   ## Summary
   
   - **Pre-size the memo table** used by `SetLookupState` from the value-set 
length.
   - Use the memo table's 50% growth threshold when choosing the initial table 
size.
   - Keep the other hash-state paths at their current zero-size hint.
   - Add a benchmark for numeric and string value sets with unique and repeated 
values.
   
   ## Benchmark
   
   Apple M1 Pro. Compared with main at `6b039a76`.
   
   For a 64K unique value set:
   
   | Case | Main B/op | This change B/op | Main allocs/op | This change 
allocs/op |
   | --- | ---: | ---: | ---: | ---: |
   | int64 | 8.66 MB | 3.41 MB | 58 | 52 |
   | string | 10.13 MB | 6.56 MB | 64,099 | 64,062 |
   
   The main benefit is avoiding repeated table growth and rehashing while 
building a large lookup set.
   
   ## Checks
   
   - `go test ./arrow/compute/... -count=1`
   - `go test -race ./arrow/compute/...`
   - `go vet ./arrow/compute/internal/kernels`
   


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