In lucene 8.4 (Elasticsearch 7.6.2), all indices are enabled with soft-deletes. We found the TieredMergePolicy contains redundant query computation to acquire numDeletesToMerge for findMerges. According to code from getSortedBySegmentSize , I think we should reuse the result of numDeletesToMerge which can reduce 3% CPU and some IO overheads.

 
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Migrated from LUCENE-10041 by Feng Gui, updated Aug 16 2021
Attachments: IMG21.jpeg