Formal models and scripts: codecreader-wrappers

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

• SlowCompositeCodecReaderWrapper's merged vector iterator numbers ordinals by position and ignores each input's own index(), so addIndexes of two or more SortingCodecReader inputs through a reordering merge policy writes vectors onto the wrong documents (finding LFV-278; repro · finding page)
• A reordered addIndexes(CodecReader...) silently drops the stored fields and term vectors of the first document after an empty (maxDoc 0) input reader: SlowCompositeCodecReaderWrapper.docIdToReaderId keeps an Arrays.binarySearch hit on a repeated doc start and reads that document from the empty reader (finding LFV-318; repro · finding page)
• addIndexes(CodecReader...) with the default config rejects inputs whose maxDoc() sum, deleted documents included, exceeds MAX_DOCS although only their live documents are added, because it always builds a merged view of the inputs for OneMerge#reorder (regression since 9.9.0) (finding LFV-285; repro · finding page)

Files

• addindexes-merged-view-total-maxdoc-limit/model/leaf_lookup_smt.py (used for LFV-285)
• merged-vector-iterator-ignores-sub-ord/model/leaf_lookup_smt.py (used for LFV-278)
• slowcomposite-docid-lookup-empty-leaf/model/leaf_lookup_smt.py (used for LFV-318)

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.