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REQ: check each compactor's lgWeight against its level - #788
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ReqSketch.heapify() accepted any lgWeight byte. The sketch creates the compactor at level h with lgWeight h, so any other value is corrupt. It does not fail later: the sorted view weights the compactor's items by 1L << lgWeight, so a wrong value silently changes ranks and quantiles. Check that compactor i has lgWeight i, in exact and estimation mode. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
tisonkun
approved these changes
Nov 1, 2026
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Problem
ReqSketch.heapify()reads each compactor'slgWeightbyte without checking it. The sketch always creates the compactor at levelhwithlgWeight == h, so any other value means the image is corrupt.A wrong value doesn't cause an error later. The sorted view weights each compactor's items by
1L << lgWeight(since #787), so a corrupt byte silently changes every rank and quantile the sketch reports.Change
ReqSerDenow checks that compactorihaslgWeight == i, in both exact and estimation mode, and throwsSketchesArgumentExceptionotherwise. Valid images, including the C++ images in the cross-language tests, are unaffected.Tests
The new
ReqSerDeTest:lgWeightin the first compactor (70 and 1), in the second compactor, and in the single compactor of an exact-mode image.mvn verifypasses.🤖 Generated with Claude Code