[SPARK-57530][CORE] Make SparkFileUtils.recursiveList null-safe and linear-time#56590
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[SPARK-57530][CORE] Make SparkFileUtils.recursiveList null-safe and linear-time#56590LuciferYang wants to merge 1 commit into
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…inear-time `SparkFileUtils.recursiveList` dereferenced `File.listFiles` without a null check (it returns null on an IO error or if the directory is removed during the walk), so it could throw NullPointerException; it also used `Buffer.remove(0)` as a queue, which is O(n) and made the walk O(n^2) on wide trees. Rewrite the traversal to null-guard both `listFiles` calls (skipping and logging an unreadable directory instead of throwing) and to use a queue with O(1) dequeue, keeping it linear. Drop the now-clearly-dead `Option(...).getOrElse(Array.empty)` guard at the `RocksDBFileManager` call site, since `recursiveList` never returns null. Add `SparkFileUtilsSuite`.
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What changes were proposed in this pull request?
SparkFileUtils.recursiveListwalks a directory tree by readingFile.listFilesand draining a buffer used as a work queue. Two problems:listFileswithout a null check.File.listFilesreturns null when a directory cannot be read (an IO error, or the directory being removed during the walk), so the walk could throwNullPointerException.Buffer.remove(0), which is O(n); on a wide tree the whole walk is O(n^2).This PR rewrites the traversal to:
listFilescalls, skipping (and logging) a directory that cannot be listed instead of throwing;Queuewith O(1) dequeue, so the walk is linear in the number of entries.It also drops the now-clearly-dead
Option(...).getOrElse(Array.empty)guard at theRocksDBFileManagercall site, sincerecursiveListnever returns null. For a readable tree the result (the set of files and directories, and the traversal order) is unchanged.Why are the changes needed?
recursiveListruns on real paths, such as the RocksDB state-store file manager andLocalSparkCluster. A directory that becomes unreadable mid-walk would crash the walk with an NPE instead of returning what it could, and the O(n^2)remove(0)is needless overhead on directories with many entries.Does this PR introduce any user-facing change?
No. For a readable directory tree the returned entries are identical; the only difference is that a directory which cannot be listed is now skipped with a warning instead of raising an internal
NullPointerException.How was this patch tested?
Added
SparkFileUtilsSuitewith three cases: a nested listing, a root whoselistFilesreturns null, and a subdirectory whoselistFilesreturns null mid-walk (with a spy confirming non-directories are not recursed into). The two null cases throw on the old code and pass with the fix.build/sbt 'common-utils/testOnly *SparkFileUtilsSuite'passes.Was this patch authored or co-authored using generative AI tooling?
Generated-by: Claude Code (Claude Opus 4.8)