db/recsplit/eliasfano32: fix searchUpperReverse off-by-one on no-solution fast path#20566
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AskAlexSharov merged 3 commits intomainfrom Apr 15, 2026
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db/recsplit/eliasfano32: fix searchUpperReverse off-by-one on no-solution fast path#20566AskAlexSharov merged 3 commits intomainfrom
AskAlexSharov merged 3 commits intomainfrom
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…tion fast path Return lo+1 instead of lo in the n<=0 branch of searchUpperReverse to mirror searchUpperForward behavior. When hiIdx==lo the answer is past the bracket (guaranteed miss), so returning lo caused searchReverse to probe idx=0 unnecessarily instead of skipping the loop entirely.
…corner case TestSearchUpperReverseNoSolution directly asserts that searchUpperReverse returns count+1 (not count) when all upper bits exceed hi, ensuring the caller loop in searchReverse is skipped. The test fails against the pre-fix code that returned lo.
Giulio2002
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LGTM \u2014 small, straightforward change with low review risk
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Fixes CR comment from #19788.
In
searchUpperReverse, then <= 0fast path (whenhiIdx == lo) returnedlo, causingsearchReverseto still probeidx=0on guaranteed-miss queries. The correct return islo + 1, mirroringsearchUpperForwardand ensuring the caller loop is skipped entirely when there is no solution.