CollationKeyFilter
converts each token into its binary CollationKey using the
provided Collator, and then encode the CollationKey
as a String using
{@link org.apache.lucene.util.IndexableBinaryStringTools}, to allow it to be
stored as an index term.
// "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);
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]);
}
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);
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):
ICUCollationKeyFilter, available in the icu package in Lucene's contrib area,
uses ICU4J's Collator, which
makes its version available, thus allowing collation to be versioned
independently from the JVM. ICUCollationKeyFilter is also
significantly faster and generates significantly shorter keys than
CollationKeyFilter. 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 CollationKeyFilter to generate index terms, do not use
ICUCollationKeyFilter on the query side, or vice versa.