Tantivy 0.13 introduce a change in the index format that will require you to reindex your index (BlockWAND information are added in the skiplist). The index size increase is minor as this information is only added for full blocks. If you have a massive index for which reindexing is not an option, please contact me so that we can discuss possible solutions.

• Bugfix in FuzzyTermQuery not matching terms by prefix when it should (@Peachball)
• Relaxed constraints on the custom/tweak score functions. At the segment level, they can be mut, and they are not required to be Sync + Send.
• MMapDirectory::open does not return a Result anymore.
• Change in the DocSet and Scorer API. (@fulmicoton). A freshly created DocSet point directly to their first doc. A sentinel value called TERMINATED marks the end of a DocSet. .advance() returns the new DocId. Scorer::skip(target) has been replaced by Scorer::seek(target) and returns the resulting DocId. As a result, iterating through DocSet now looks as follows

let mut doc = docset.doc();
while doc != TERMINATED {
   // ...
   doc = docset.advance();
}

The change made it possible to greatly simplify a lot of the docset's code.

• Misc internal optimization and introduction of the Scorer::for_each_pruning function. (@fulmicoton)
• Added an offset option to the Top(.*)Collectors. (@robyoung)
• Added Block WAND. Performance on TOP-K on term-unions should be greatly increased. (@fulmicoton, and special thanks to the PISA team for answering all my questions!)