Finding the number of documents in a lucene index

Question

使用 Lucene 的 Java 版本，您将如何找出索引中的文档数量？

Answer 1

IndexReader contains the methods you need, in particular, numDocs

http://lucene.apache.org/core/3_6_0/api/all/org/apache/lucene/index/IndexReader.html#numDocs()

Answer 2

Using java you can find the number of documents like this :

IndexReader reader = IndexReader.open(FSDirectory.open(indexDirectory));
System.out.println(reader.maxDoc()); //this will give ya what you need.

Answer 3

官方文档： http ： //lucene.apache.org/java/2_4_0/api/org/apache/lucene/index/IndexReader.html#numDocs（）

Answer 4

When using Hibernate Search, it is possible to obtain a Lucene IndexReader instance through the Hibernate Search API and then use reader.numDocs() as already mentioned in previous answers.

FullTextEntityManager fullTextEntityManager = org.hibernate.search.jpa.Search.getFullTextEntityManager(get‌​EntityManager());
IndexReader reader = fullTextEntityManager.getSearchFactory().getIndexReaderAcces‌​sor().open(MyEntity1‌​.class, MyEntity2.class ...);
int numDocs = reader.numDocs();

Answer 5

With recent Lucene version using an IndexReader the following Kotlin snippet does the job:

DirectoryReader.open(directory).use { reader ->
    println(reader.numDocs())
}

where directory is an instance of Directory containing the index.