Nhat Nguyen d41cf6ac9f
Use delCount of SegmentInfos to calculate numDocs (#36323)
Today, we iterate the bitset of hardLiveDocs to calculate the number of
live docs. This calculation might be expensive if we enable soft-deletes
(by default) for old indices whose soft-deletes was disabled previously
and had hard-deletes.

Once soft-deletes is enabled, we no longer hard-update or hard-delete
documents directly. We have hard-deletes in two scenarios: (1) from old
segments where soft-deletes was disabled, (2) when IndexWriter hits
non-aborted exceptions. These two cases, IW flushes SegmentInfos before
exposing the hard-deletes; thus we can use the hard-delete count of
SegmentInfos.
2018-12-08 21:24:36 -05:00
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