[SPARK-53797] Improve performance of maxBytesPerTrigger for file stream sources #52515
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@MaxNevermind @viirya @dongjoon-hyun since you were the original creator/reviewers |
Kimahriman
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What changes were proposed in this pull request?
Fixes a performance issue with the new
maxBytesPerTriggeroption for file stream sources introduced in #44636. This changes the iteration of files for calculating offsets whenmaxBytesPerTriggeris used with file stream sources from list indexing to iteration.Why are the changes needed?
We tried out this new option and found streams reading for tables with a lot of files (in the millions) were spending hours trying to construct batches. After looking at the thread dump for these, I could see a Scala immutable.List was what the
filesobject was stored as, which is a linked list under the hood withO(n)lookup time by index, making thetakesFilesUntilMaxmethod aO(n^2)operation. Instead the list should simply be iterated over which makes it a simpleO(n)operation overall.Does this PR introduce any user-facing change?
No, just performance.
How was this patch tested?
No new tests, purely a performance improvement.
Was this patch authored or co-authored using generative AI tooling?
No