Lucene in Action

...Constructing Boolean queries textually via QueryParser is done using the opera- tors AND, OR, and NOT. Terms listed without an operator specified use an implicit operator, which by default is OR. The query abc xyz will be interpreted as either abc OR xyz or abc AND xyz, based on the implicit ... shortcut syntax; table 3.7 illustrates various syntax equivalents. Table 3.7 Boolean query operator ... with at least one nonnegated term to return documents; in other words, it isn't possible to use a query like... [Full sample chapter]

... and store each such bag of sequences as a Lucene document. Queries are similarly parsed into bags of character subse- quences from which boolean query clauses are formed. The hits resulting from a query term will be the documents representing the terms in order of their fuzzy string similarity to the query ... 2 to 4: "Al", "l ", " J", ..., "ah", ..., "Al Ja", "l Ja", " Jaz", ..., "erah" Used as a query, "Al Jazeerah ... used in a query for "Al Jazeerah" Score Result 999 Al Jazeerah 787 Al Jazeera 406 Jazeera...

... to a BooleanQuery using this API method: public void add(Query query, boolean required, boolean ... with a "2004" PrefixQuery.) d Here we combine the two queries into a single boolean query with both ... a Boolean- Clause, and the other accepts a Query and two boolean flags. A BooleanClause is a container of a query ... The various query types discussed here can be combined in complex ways using BooleanQuery. BooleanQuery itself is a container of Boolean clauses. A clause is a subquery that can be optional, required... [Full sample chapter]

... has a different weight. The Nutch Query Handler generates a Lucene boolean query that contains ... The Query Handler asks each Index Searcher for only a small number of documents (usually 10). Since ... one source, especially when users rarely move beyond the first page of results. Each user query is actually expanded to quite a complicated Lucene query before it is processed.2 Each indexed document ... of multiword queries, which would require a limited amount of integration. 2 Authors' note: See more...

... and developer mailing list discussions. Egothor supports an extended Boolean model, which allows it to function as both the pure Boolean model and the Vector model. You can tune which model to use via a simple query-time parameter. This software features a number of dif- ferent query types, supports similar search syntax, and allows multithreaded querying, which can come in handy if you're working ... of queries and has a query parser that supports human-friendly search syntax; stemmers based... [Full sample chapter]

... range queries inclusive of the begin and end terms: public class RangeQueryTest extends LiaTestCase ... (); } public void testInclusive() throws Exception { RangeQuery query = new RangeQuery(begin, end, true); IndexSearcher searcher = new IndexSearcher(directory); Hits hits = searcher.search(query); assertEquals ... to construct a RangeQuery is a boolean flag indicating whether the range is inclusive. Using the same ... Exception { RangeQuery query = new RangeQuery(begin, end, false); IndexSearcher searcher = new IndexSearcher... [Full sample chapter]

... 6, syn- onym injection in chapter 4, and the Boolean logic in this chapter. In this chapter, we'll limit ... methods. Query (and Concrete subclasses encapsulate logic for a particular query type. Instances of subclasses) Query are passed to an IndexSearcher's search method. QueryParser Processes a human-entered (and readable) expression into a concrete Query object. Hits Provides access to search results. Hits is returned from IndexSearcher's search method. When you're querying a Lucene index, an ordered... [Full sample chapter]

..., boosting it would boost all matched documents equally. In a multiple-clause boolean query, some documents ... . Figure 3.1 Lucene uses this formula to determine a document score based on a query. Table ... (q, d) Coordination factor, based on the number of query terms the document contains. queryNorm(q) Normalization value for a query, given the sum of the squared weights of each of the query terms. Boost factors are built into the equation to let you affect a query or field's influ- ence on score. Field boosts... [Full sample chapter]

..., we chose the Boolean query 'lucene AND NOT slow', which finds all files that contain the word lucene ... arguments: The path to the index created with Indexer A query to use to search the index Listing 1.2 Searcher: searches a Lucene index for a query passed as an argument /** * This code was originally ... " + Searcher.class.getName() + " <query>"); } Index directory File indexDir = new File(args[0]); created by Indexer String q = args[1]; Query string if (!indexDir.exists() || !indexDir... [Full sample chapter]

... that they are added to the boolean query as optional terms that are neither required nor prohibited ... . We employ the same n-gram extractor, converting the n-gram tokens into term query clauses: public static ... the IndexSearcher to build in the n-gram query parser: public static class NGramSearcher extends ... and result ordering. Here's an example of some of the queries run over 1,307 newswire docu- ments ... as a query. Total processing time was under two minutes on a modest personal computer, including the time...

...(directory); } private boolean matched(String[] phrase, int slop) throws IOException { PhraseQuery query = new PhraseQuery(); query.setSlop(slop); for (int i=0; i < phrase.length; i++) { query.add(new Term("field", phrase[i])); } Hits hits = searcher.search(query); return hits.length() > 0; } } Because we want to demonstrate several phrase query examples, we wrote the matched method to simplify ... a phrase query matched the test document: public class PhraseQueryTest extends TestCase { private... [Full sample chapter]

... of query is desired, override this method. For example, a SpanNearQuery can replace PhraseQuery ... , int slop) getFuzzyQuery(String field, Fuzzy queries can adversely affect performance. Override and throw a String termStr) ParseException to disallow fuzzy queries. getPrefixQuery(String field, This method is used to construct a query when the term ends with an String termStr) asterisk. The term ... this method to perform any desired analysis. getRangeQuery(String field, Default range-query behavior has...

..., we use Lucene's bool- ean query capability and the information from one book to look up other books ... before books by other authors. e Using the terms from the subject term vectors, we add each to a boolean query. f We combine the author and subject queries into a final boolean query. g We exclude ... likeThisQuery = new BooleanQuery(); f Create final likeThisQuery.add(authorQuery, false, false); query ... ( current book new Term("isbn", doc.get("isbn"))), false, true); //System.out.println(" Query...

... integers for range queries. The desired effect is shown in the following test: public void ... StandardAnalyzer()); Query query = parser.parse("last-modified:[1/1/04 TO 2/29/04]"); assertEquals("last-modified:[20040101 TO 20040229]", query.toString("contents")); } Now that we have our desired ... analyzer) { super(field, analyzer); } protected Query getRangeQuery(String field, Analyzer analyzer, String part1, String part2, boolean inclusive) throws ParseException { try { DateFormat df = DateFormat...

... itself. You could try to use bool- ean queries to make sure that a search finds a good match ... for date-range queries. createddate_range Field.Keyword Date as a String with the format YYYYMMDD. Used for date-range queries. We created a simple Java representation of this data, SearchContentHolder, which ... an incremental build, then the results are simply limited by the SQL query that we issue to get the content ... postings with a common subject. 13 Authors' note: For more on querying multiple fields...

... up to you. In this section, our example scenario indexes an integer id field so that range queries can ... (); } } With this index-time padding, we're only halfway there. A query expression for IDs 37 through ... the getRangeQuery() method: protected Query getRangeQuery(String field, Analyzer analyzer, String part1, String part2, boolean inclusive) throws ParseException { if ("id".equals(field)) { try { int num ... shows that the range query worked as expected, and you can see the results of the padding using Query...

... that bypasses tokenization and is indexed exactly as is as a single term. It's also straightforward to query ... and attempt to query on Field.Keyword-created fields. The "keyword"-ness of a field is only known during ... { Query query = new TermQuery(new Term("partnum", "Q36")); No analysis Hits hits = searcher.search(query ... a document and can retrieve it using a TermQuery. But what happens if we generate a query using QueryParser? public void testBasicQueryParser() throws Exception { Query query = QueryParser.parse...

..., phrase, and Boolean queries and weights them based on their correspond- ing boost factor. A query must ... 1.1, includes up to three lines of the match- ing document highlighting the terms of the query. Often ... to highlight text based on a Lucene query. Figure 8.17 is an example of using Highlighter on a sample of text based on a term query for ipsum. The Highlighter code has recently evolved substantially ... the lazy dog"; TermQuery query = new TermQuery(new Term("field", "fox")); Scorer scorer = new QueryScorer...

... that Directory to the IndexSearcher class and then find Documents that match a given query by passing search terms encapsulated in the Query object to one of IndexSearcher's search methods. The results ... to specify it. However, if you like explicit code, you can call the setUse- Compound(boolean) method ... 's set- UseCompoundFiles(boolean) method at any time during indexing; the next time Lucene merges index segments ... in a new format specified via the setUseCompoundFile(boolean) method. B.3 Choosing the index...