Lucene: Multifield searches

We can run multifield searches in Lucene using either the BooleanQuery API or using the MultiFieldQueryParser for parsing the query text. For e.g. If a index has 2 fields FirstName and LastName and if you need to search for "John" in the FirstName field and "Travis" in the LastName field one can use a Boolean Query as such:

   1: BooleanQuery bq = new BooleanQuery();

   2: Query qf = new TermQuery(new Lucene.Net.Index.Term("FirstName", "John"));

   3: Query ql = new TermQuery(new Lucene.Net.Index.Term("LastName", "Travis"));

   4: bq.Add(qf, BooleanClause.Occur.MUST);

   5: bq.Add(ql, BooleanClause.Occur.MUST);

   6: IndexSearcher srchr = new IndexSearcher(@"C:\indexDir");

   7: srchr.Search(bq);

Now if we need to search a single term across either of the FirstName and LastName fields then we can use the MultiFieldQueryParser as follows:

   1: Query query = MultiFieldQueryParser.parse("commonName", new String[] { "FirstName", "LastName" },new SimpleAnalyzer());

   2: srchr.Search(query);

Now if you need to search the term that must exist in both the fields then we use the following:

   1: Query query = MultiFieldQueryParser.Parse("commonName",

   2:                         new String[] { "FirstName", "LastName" },

   3:                         new BooleanClause.Occur[] { BooleanClause.Occur.MUST,BooleanClause.Occur.MUST},

   4:                         new SimpleAnalyzer());

   5: srchr.Search(query);

Finally if you don’t want a term to occur in one of the Fields (say FirstName) then use:

   1:  

   2:                 Query query = MultiFieldQueryParser.Parse("commonName",

   3:                                         new String[] { "FirstName", "LastName" },

   4:                                         new BooleanClause.Occur[] { BooleanClause.Occur.MUST_NOT,BooleanClause.Occur.MUST},

   5:                                         new SimpleAnalyzer());

   6:                 srchr.Search(query);

so if you need to search a single term across multiple fields then use MultiFieldQueryParser, if you need to search different terms in different fields then use the BooleanQuery as shown first

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