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-<html>
-<head>
- <title>Lucene Collation Package</title>
-</head>
-<body>
-<p>
- <code>CollationKeyFilter</code>
- converts each token into its binary <code>CollationKey</code> using the
- provided <code>Collator</code>, and then encode the <code>CollationKey</code>
- as a String using
- {@link org.apache.lucene.util.IndexableBinaryStringTools}, to allow it to be
- stored as an index term.
-</p>
-
-<h2>Use Cases</h2>
-
-<ul>
- <li>
- Efficient sorting of terms in languages that use non-Unicode character
- orderings. (Lucene Sort using a Locale can be very slow.)
- </li>
- <li>
- Efficient range queries over fields that contain terms in languages that
- use non-Unicode character orderings. (Range queries using a Locale can be
- very slow.)
- </li>
- <li>
- Effective Locale-specific normalization (case differences, diacritics, etc.).
- ({@link org.apache.lucene.analysis.LowerCaseFilter} and
- {@link org.apache.lucene.analysis.ASCIIFoldingFilter} provide these services
- in a generic way that doesn't take into account locale-specific needs.)
- </li>
-</ul>
-
-<h2>Example Usages</h2>
-
-<h3>Farsi Range Queries</h3>
-<pre class="prettyprint">
- // "fa" Locale is not supported by Sun JDK 1.4 or 1.5
- Collator collator = Collator.getInstance(new Locale("ar"));
- CollationKeyAnalyzer analyzer = new CollationKeyAnalyzer(collator);
- RAMDirectory ramDir = new RAMDirectory();
- IndexWriter writer = new IndexWriter
- (ramDir, analyzer, true, IndexWriter.MaxFieldLength.LIMITED);
- Document doc = new Document();
- doc.add(new Field("content", "\u0633\u0627\u0628",
- Field.Store.YES, Field.Index.ANALYZED));
- writer.addDocument(doc);
- writer.close();
- IndexSearcher is = new IndexSearcher(ramDir, true);
-
- // The AnalyzingQueryParser in Lucene's contrib allows terms in range queries
- // to be passed through an analyzer - Lucene's standard QueryParser does not
- // allow this.
- AnalyzingQueryParser aqp = new AnalyzingQueryParser("content", analyzer);
- aqp.setLowercaseExpandedTerms(false);
-
- // Unicode order would include U+0633 in [ U+062F - U+0698 ], but Farsi
- // orders the U+0698 character before the U+0633 character, so the single
- // indexed Term above should NOT be returned by a ConstantScoreRangeQuery
- // with a Farsi Collator (or an Arabic one for the case when Farsi is not
- // supported).
- ScoreDoc[] result
- = is.search(aqp.parse("[ \u062F TO \u0698 ]"), null, 1000).scoreDocs;
- assertEquals("The index Term should not be included.", 0, result.length);
-</pre>
-
-<h3>Danish Sorting</h3>
-<pre class="prettyprint">
- Analyzer analyzer
- = new CollationKeyAnalyzer(Collator.getInstance(new Locale("da", "dk")));
- RAMDirectory indexStore = new RAMDirectory();
- IndexWriter writer = new IndexWriter
- (indexStore, analyzer, true, IndexWriter.MaxFieldLength.LIMITED);
- String[] tracer = new String[] { "A", "B", "C", "D", "E" };
- String[] data = new String[] { "HAT", "HUT", "H\u00C5T", "H\u00D8T", "HOT" };
- String[] sortedTracerOrder = new String[] { "A", "E", "B", "D", "C" };
- for (int i = 0 ; i < data.length ; ++i) {
- Document doc = new Document();
- doc.add(new Field("tracer", tracer[i], Field.Store.YES, Field.Index.NO));
- doc.add(new Field("contents", data[i], Field.Store.NO, Field.Index.ANALYZED));
- writer.addDocument(doc);
- }
- writer.close();
- Searcher searcher = new IndexSearcher(indexStore, true);
- Sort sort = new Sort();
- sort.setSort(new SortField("contents", SortField.STRING));
- Query query = new MatchAllDocsQuery();
- ScoreDoc[] result = searcher.search(query, null, 1000, sort).scoreDocs;
- for (int i = 0 ; i < result.length ; ++i) {
- Document doc = searcher.doc(result[i].doc);
- assertEquals(sortedTracerOrder[i], doc.getValues("tracer")[0]);
- }
-</pre>
-
-<h3>Turkish Case Normalization</h3>
-<pre class="prettyprint">
- Collator collator = Collator.getInstance(new Locale("tr", "TR"));
- collator.setStrength(Collator.PRIMARY);
- Analyzer analyzer = new CollationKeyAnalyzer(collator);
- RAMDirectory ramDir = new RAMDirectory();
- IndexWriter writer = new IndexWriter
- (ramDir, analyzer, true, IndexWriter.MaxFieldLength.LIMITED);
- Document doc = new Document();
- doc.add(new Field("contents", "DIGY", Field.Store.NO, Field.Index.ANALYZED));
- writer.addDocument(doc);
- writer.close();
- IndexSearcher is = new IndexSearcher(ramDir, true);
- QueryParser parser = new QueryParser("contents", analyzer);
- Query query = parser.parse("d\u0131gy"); // U+0131: dotless i
- ScoreDoc[] result = is.search(query, null, 1000).scoreDocs;
- assertEquals("The index Term should be included.", 1, result.length);
-</pre>
-
-<h2>Caveats and Comparisons</h2>
-<p>
- <strong>WARNING:</strong> Make sure you use exactly the same
- <code>Collator</code> at index and query time -- <code>CollationKey</code>s
- are only comparable when produced by
- the same <code>Collator</code>. Since {@link java.text.RuleBasedCollator}s
- are not independently versioned, it is unsafe to search against stored
- <code>CollationKey</code>s unless the following are exactly the same (best
- practice is to store this information with the index and check that they
- remain the same at query time):
-</p>
-<ol>
- <li>JVM vendor</li>
- <li>JVM version, including patch version</li>
- <li>
- The language (and country and variant, if specified) of the Locale
- used when constructing the collator via
- {@link java.text.Collator#getInstance(java.util.Locale)}.
- </li>
- <li>
- The collation strength used - see {@link java.text.Collator#setStrength(int)}
- </li>
-</ol>
-<p>
- <code>ICUCollationKeyFilter</code>, available in the icu package in Lucene's contrib area,
- uses ICU4J's <code>Collator</code>, which
- makes its version available, thus allowing collation to be versioned
- independently from the JVM. <code>ICUCollationKeyFilter</code> is also
- significantly faster and generates significantly shorter keys than
- <code>CollationKeyFilter</code>. See
- <a href="http://site.icu-project.org/charts/collation-icu4j-sun"
- >http://site.icu-project.org/charts/collation-icu4j-sun</a> for key
- generation timing and key length comparisons between ICU4J and
- <code>java.text.Collator</code> over several languages.
-</p>
-<p>
- <code>CollationKey</code>s generated by <code>java.text.Collator</code>s are
- not compatible with those those generated by ICU Collators. Specifically, if
- you use <code>CollationKeyFilter</code> to generate index terms, do not use
- <code>ICUCollationKeyFilter</code> on the query side, or vice versa.
-</p>
-<pre>
-</pre>
-</body>
-</html>
fnp / pylucene.git / blobdiff