Formal models and scripts: ascii-folding-table-vs-unicode-character-database

Tools: Python

These are the working models and scripts this part of the hunt used. Some encode the code as it is (a counterexample is the expected result), others a fixed or correct variant; read the header comment of each file. Paths inside them were replaced by placeholders such as $LUCENE (a Lucene checkout) and $WORK.

Findings

• ASCIIFoldingFilter folds six letters to the ASCII letter of the opposite case (ǥ U+01E5 and ǧ U+01E7 to 'G', insular ꞅ U+A785 to 'S' and Ꞅ U+A784 to 's', Ɐ U+2C6F to 'a', Ꜿ U+A73E to 'c'; stretched ʗ U+0297 to 'C' is contested), so a LowerCaseFilter-then-ASCIIFoldingFilter chain indexes 'naǧib' as 'naGib' and the ASCII query 'nagib' finds nothing (finding LFV-818; repro · finding page)

Files

• asciifolding-table-letters-in-wrong-case-group/model/move_cases.py (used for LFV-818)

How to run

• Python: python3 <file>.py; scripts that import z3 need the z3-solver package.

Snapshot of 2026-11-03. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.