/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /** * Unicode collation support. *

* Collation converts each token into its binary CollationKey * using the provided Collator, allowing it to be stored as an index term. *

* *

Use Cases

* * * *

Example Usages

* *

Farsi Range Queries

* 
 *   // "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, new IndexWriterConfig(analyzer));
 *   Document doc = new Document();
 *   doc.add(new TextField("content", "\u0633\u0627\u0628", Field.Store.YES));
 *   writer.addDocument(doc);
 *   writer.close();
 *   IndexReader ir = DirectoryReader.open(ramDir);
 *   IndexSearcher is = new IndexSearcher(ir);
 * 
 *   QueryParser aqp = new QueryParser("content", analyzer);
 *   aqp.setAnalyzeRangeTerms(true);
 *     
 *   // 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);
 *
* *

Danish Sorting

* 
 *   Analyzer analyzer 
 *     = new CollationKeyAnalyzer(Collator.getInstance(new Locale("da", "dk")));
 *   RAMDirectory indexStore = new RAMDirectory();
 *   IndexWriter writer = new IndexWriter(indexStore, new IndexWriterConfig(analyzer));
 *   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 StoredField("tracer", tracer[i]));
 *     doc.add(new TextField("contents", data[i], Field.Store.NO));
 *     writer.addDocument(doc);
 *   }
 *   writer.close();
 *   IndexReader ir = DirectoryReader.open(indexStore);
 *   IndexSearcher searcher = new IndexSearcher(ir);
 *   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]);
 *   }
 *
* *

Turkish Case Normalization

* 
 *   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, new IndexWriterConfig(analyzer));
 *   Document doc = new Document();
 *   doc.add(new TextField("contents", "DIGY", Field.Store.NO));
 *   writer.addDocument(doc);
 *   writer.close();
 *   IndexReader ir = DirectoryReader.open(ramDir);
 *   IndexSearcher is = new IndexSearcher(ir);
 *   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);
 *
* *

Caveats and Comparisons

*

* WARNING: Make sure you use exactly the same * Collator at index and query time -- CollationKeys * are only comparable when produced by * the same Collator. Since {@link java.text.RuleBasedCollator}s * are not independently versioned, it is unsafe to search against stored * CollationKeys 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): *

*
    *
  1. JVM vendor
    2. *
  2. JVM version, including patch version
    3. *
  3. * 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)}. *
    4. *
  4. * The collation strength used - see {@link java.text.Collator#setStrength(int)} *
    5. *
*

* ICUCollationKeyAnalyzer, available in the icu analysis module, * uses ICU4J's Collator, which * makes its version available, thus allowing collation to be versioned * independently from the JVM. ICUCollationKeyAnalyzer is also * significantly faster and generates significantly shorter keys than * CollationKeyAnalyzer. See * http://site.icu-project.org/charts/collation-icu4j-sun for key * generation timing and key length comparisons between ICU4J and * java.text.Collator over several languages. *

*

* CollationKeys generated by java.text.Collators are * not compatible with those those generated by ICU Collators. Specifically, if * you use CollationKeyAnalyzer to generate index terms, do not use * ICUCollationKeyAnalyzer on the query side, or vice versa. *

*/ package org.apache.lucene.collation;