How to sort Numeric field in Lucene 6

Question

I want to sort my search result based on a numeric field. In the following example code, I want to sort based on the 'age' field. I start from using the answers from:

[How to sort IntPont or LongPoint field in Lucene 6

But it does sort based SCORE. The age are still not ascending.

And

[Sorting search result in Lucene based on a numeric field

I changed SortField.Type.SCORE to SortField.Type.LONG in the search function. But I get:

unexpected docvalues type NONE for field 'age' (expected=NUMERIC)

Here my code:

public class TestLongPointSort {


    public static void main(String[] args) throws Exception {

        String indexPath = "/tmp/testSort";
        Analyzer standardAnalyzer = new StandardAnalyzer();
        Directory indexDir = FSDirectory.open(Paths.get(indexPath));
        IndexWriterConfig iwc = new IndexWriterConfig(standardAnalyzer);

        iwc.setOpenMode(IndexWriterConfig.OpenMode.CREATE_OR_APPEND);

        IndexWriter masterIndex = new IndexWriter(indexDir, iwc);

        Document doc = new Document();

        String name = "bob";
        doc.add(new TextField("name", name, Field.Store.YES));
        doc.add(new SortedDocValuesField("name", new BytesRef(name)));
        doc.add(new SortedNumericDocValuesField("age", 20L));
        doc.add(new StoredField("age", 20L));
        long ts = System.currentTimeMillis();
        doc.add(new SortedNumericDocValuesField("ts", ts));
        doc.add(new StoredField("ts", ts));
        masterIndex.addDocument(doc);
        Thread.sleep(1);

        name = "max";
        doc = new Document();
        doc.add(new TextField("name", name, Field.Store.YES));
        doc.add(new SortedDocValuesField("name", new BytesRef(name)));
        doc.add(new SortedNumericDocValuesField("age", 19L));
        doc.add(new StoredField("age", 19L));
        ts = System.currentTimeMillis();
        doc.add(new SortedNumericDocValuesField("ts", ts));
        doc.add(new StoredField("ts", ts));
        masterIndex.addDocument(doc);
        Thread.sleep(1);

        name = "jim";
        doc = new Document();
        doc.add(new TextField("name", name, Field.Store.YES));
        doc.add(new SortedDocValuesField("name", new BytesRef(name)));
        doc.add(new SortedNumericDocValuesField("age", 21L));
        doc.add(new StoredField("age", 21L));
        ts = System.currentTimeMillis();
        doc.add(new SortedNumericDocValuesField("ts", ts));
        doc.add(new StoredField("ts", ts));
        masterIndex.addDocument(doc);

        masterIndex.commit();
        masterIndex.close();

        IndexReader reader = DirectoryReader.open(FSDirectory.open(Paths.get(indexPath)));
        IndexSearcher searcher = new IndexSearcher(reader);

        Analyzer analyzer = new KeywordAnalyzer();
        QueryParser queryParser = new QueryParser("message", analyzer);

        Sort sort;
        TopDocs docs;
        sort = new Sort(new SortField("name", SortField.Type.STRING));
        docs = searcher.search(new MatchAllDocsQuery(), 100, sort);
        System.out.println("Sorted by name");
        for (ScoreDoc scoreDoc : docs.scoreDocs) {
            Document doc2 = searcher.doc(scoreDoc.doc);
            System.out.println("Name:" + doc2.get("name") + " ; age:" + doc2.get("age") + " ; ts:" + doc2.get("ts"));
        }

        //docs = searcher.search(new MatchAllDocsQuery(), 100, new Sort(new SortField("age", SortField.Type.SCORE, true)));
        docs = searcher.search(new MatchAllDocsQuery(), 100, new Sort(new SortField("age", SortField.Type.LONG, true)));
        System.out.println("Sorted by age");
        for (ScoreDoc scoreDoc : docs.scoreDocs) {

            Document doc2 = searcher.doc(scoreDoc.doc);
            System.out.println("Name:" + doc2.get("name") + " ; age:" + doc2.get("age") + " ; ts:" + doc2.get("ts"));
        }

        reader.close();

    }
}

As we can see, sorting STRING is good but I didn't figure out how I can get my numbers (LONG) sorted.

What is the right way to sort Numeric fields?

Thanks

Answer 1

To sort search results using a SortedNumericDocValuesField, you'll need to use a SortedNumericSortField:

Sort sort = new Sort(new SortedNumericSortField("age", SortField.Type.LONG, true));
TopDocs docs = searcher.search(new MatchAllDocsQuery(), 100, sort);