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5.2.2. Result Size

Some use cases require information about the total number of matching documents. Consider the following examples:
Retrieving all matching documents is costly in terms of resources. The Lucene-based Query API retrieves all matching documents regardless of pagination parameters. Since it is costly to retrieve all the matching documents, the Lucene-based Query API can retrieve the total number of matching documents regardless of the pagination parameters. All matching elements are retrieved without triggering any object loads.

Example 5.8. Determining the Result Size of a Query

CacheQuery cacheQuery = Search.getSearchManager(cache).getQuery(luceneQuery,
Book.class);
//return the number of matching books without loading a single one
assert 3245 == query.getResultSize(); 

CacheQuery cacheQueryLimited =
Search.getSearchManager(cache).getQuery(luceneQuery, Book.class);
query.setMaxResult(10);
List results = query.list();
assert 10 == results.size()
//return the total number of matching books regardless of pagination
assert 3245 == query.getResultSize();
The number of results is an approximation if the index is not correctly synchronized with the database. An ansychronous cluster is an example of this scenario.
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