[PR] perf(name_mapping): reduce allocations for wide mapping updates [iceberg-go]

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

fallintoplace opened a new pull request, #2267:
URL: https://github.com/apache/iceberg-go/pull/2267

   ## What
   Speed up `UpdateNameMapping` for wide schemas.
   
   ## Why
   Large mappings create many temporary slices and field ID allocations.
   
   ## Implementation
   - Build each sibling level in one pass.
   - Keep copied field IDs in one owned slice.
   - Reuse fresh slices when aliases or fields move.
   - Preserve independent results and existing mapping behavior.
   
   ## Benchmark
   Go 1.26.3, Apple M1 Pro, `GOMAXPROCS=1`; 10 runs of 300 ms. Same benchmark file at base and head. Base: `a4fb4d0`; head: `13e98d2`.
   
   | Metric | Before | After | Change |
   | --- | ---: | ---: | ---: |
   | 4,096 fields, no updates | 873.8 µs | 404.0 µs | -53.8% |
   | 4,096 fields, rename reused | 930.3 µs | 492.4 µs | -47.1% |
   | 4,096 fields, add reused | 1,341.9 µs | 698.9 µs | -47.9% |
   | 4,096 fields, bytes/op (no updates) | 1,127.8 KiB | 384.0 KiB | -66.0% |
   | 4,096 fields, allocs/op (no updates) | 8,209 | 4,098 | -50.1% |
   
   At 2 fields, reused rename was 7.6% faster, but bytes/op increased by 64 B (448 to 512 B).
   
   Command: `GOMAXPROCS=1 go test . -run '^$' -bench '^BenchmarkUpdateNameMapping/(no-updates|rename-reused|add-reused)/(4096|2)$' -benchmem -benchtime=300ms -count=10 -cpu=1`
   


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Re: [PR] perf(name_mapping): reduce allocations for wide mapping updates [iceberg-go]

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

zeroshade merged PR #2267:
URL: https://github.com/apache/iceberg-go/pull/2267


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