j1wonpark opened a new pull request, #4146:
URL: https://github.com/apache/amoro/pull/4146

   ## Why are the changes needed?
   
   `NodeFileScanTask.dataTasks()` creates a new `ArrayList` via 
`Stream.concat().collect(toList())` on every call, even though the contents are 
immutable after construction. This method is called repeatedly in hot paths -- 
`BasicKeyedTableScan.split()` (2x), `AbstractKeyedDataReader.readData()`, and 
`readDeletedData()` (2x) -- causing unnecessary object allocation and GC 
pressure during scan operations.
   
   ## Brief change log
   
   - Added lazy caching to `NodeFileScanTask.dataTasks()` with a 
`cachedDataTasks` field
   - Wrapped the cached result with `Collections.unmodifiableList()` to prevent 
external mutation
   - Added cache invalidation (`cachedDataTasks = null`) in `addFile()` to 
ensure correctness when tasks are added after construction
   
   ## How was this patch tested?
   
   - [x] Add some test cases that check the changes thoroughly including 
negative and positive cases if possible
   
   - [ ] Add screenshots for manual tests if appropriate
   
   - [x] Run test locally before making a pull request
   
   ## Documentation
   
   - Does this pull request introduce a new feature? no
   - If yes, how is the feature documented? not applicable


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