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5.3. Filters

Apache Lucene is able to filter query results according to a custom filtering process. This is a powerful way to apply additional data restrictions, especially since filters can be cached and reused. Applicable use cases include:

security
temporal data (example, view only last month's data)
population filter (example, search limited to a given category)
and many more

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5.3.1. Defining and Implementing a Filter
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The Lucene-based Query API includes transparent caches named filters which include parameters. The API is similar to the Hibernate Core filters:

Example 5.9. Enabling Fulltext Filters for a Query

cacheQuery = Search.getSearchManager(cache).getQuery(query, Driver.class);
cacheQuery.enableFullTextFilter("bestDriver");
cacheQuery.enableFullTextFilter("security").setParameter( "login", "andre" );
cacheQuery.list(); //returns only best drivers where andre has credentials

cacheQuery = Search.getSearchManager(cache).getQuery(query, Driver.class);
cacheQuery.enableFullTextFilter("bestDriver");
cacheQuery.enableFullTextFilter("security").setParameter( "login", "andre" );
cacheQuery.list(); //returns only best drivers where andre has credentials

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In the provided example, two filters are enabled in the query. Enable or disable filters to customize the query.

Declare filters using the @FullTextFilterDef annotation. This annotation applies to @Indexed entities irrespective of the filter's query. Filter definitions are global therefore each filter must have a unique name. If two @FullTextFilterDef annotations with the same name are defined, a SearchException is thrown. Each named filter must specify its filter implementation.

Example 5.10. Defining and Implementing a Filter

@FullTextFilterDefs( {
    @FullTextFilterDef(name = "bestDriver", impl = BestDriversFilter.class), 
    @FullTextFilterDef(name = "security", impl = SecurityFilterFactory.class) 
})
public class Driver { ... }

@FullTextFilterDefs( {
    @FullTextFilterDef(name = "bestDriver", impl = BestDriversFilter.class), 
    @FullTextFilterDef(name = "security", impl = SecurityFilterFactory.class) 
})
public class Driver { ... }

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public class BestDriversFilter extends org.apache.lucene.search.Filter {

    public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
        OpenBitSet bitSet = new OpenBitSet( reader.maxDoc() );
        TermDocs termDocs = reader.termDocs( new Term( "score", "5" ) );
        while ( termDocs.next() ) {
            bitSet.set( termDocs.doc() );
        }
        return bitSet;
    }
}

public class BestDriversFilter extends org.apache.lucene.search.Filter {

    public DocIdSet getDocIdSet(IndexReader reader) throws IOException {
        OpenBitSet bitSet = new OpenBitSet( reader.maxDoc() );
        TermDocs termDocs = reader.termDocs( new Term( "score", "5" ) );
        while ( termDocs.next() ) {
            bitSet.set( termDocs.doc() );
        }
        return bitSet;
    }
}

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BestDriversFilter is a Lucene filter that reduces the result set to drivers where the score is 5. In the example, the filter implements the org.apache.lucene.search.Filter directly and contains a no-arg constructor.

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5.3. Filters

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5.3.1. Defining and Implementing a Filter
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