Java has both int (32 bit) and long (64 bit) types. What did you refer to as &#x27;native&#x27;?<p>Lucene, the popular core search library, has always used int as internal document IDs. As a result, the number of documents in one Lucene index is limited to 2 billions (Java int are signed). It&#x27;s even worse if there are many deleted docs in the index as they are are just marked as deleted and consume up IDs. There are a number of reasons why no one is keen on moving internal docIDs to long, and performance is one of them.