Add KeywordField and StringValueFacetCounts example (#12817)

lucene/demo/src/java/org/apache/lucene/demo/facet/StringValueFacetCountsExample.java

@@ -0,0 +1,133 @@
+/*
+ * 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.
+ */
+package org.apache.lucene.demo.facet;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+import org.apache.lucene.analysis.core.WhitespaceAnalyzer;
+import org.apache.lucene.document.Document;
+import org.apache.lucene.document.Field;
+import org.apache.lucene.document.KeywordField;
+import org.apache.lucene.document.SortedDocValuesField;
+import org.apache.lucene.facet.FacetResult;
+import org.apache.lucene.facet.Facets;
+import org.apache.lucene.facet.FacetsCollector;
+import org.apache.lucene.facet.FacetsConfig;
+import org.apache.lucene.facet.StringDocValuesReaderState;
+import org.apache.lucene.facet.StringValueFacetCounts;
+import org.apache.lucene.index.DirectoryReader;
+import org.apache.lucene.index.IndexWriter;
+import org.apache.lucene.index.IndexWriterConfig;
+import org.apache.lucene.index.IndexWriterConfig.OpenMode;
+import org.apache.lucene.search.IndexSearcher;
+import org.apache.lucene.search.MatchAllDocsQuery;
+import org.apache.lucene.store.ByteBuffersDirectory;
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.util.BytesRef;
+
+/**
+ * Demonstrate the use of {@link StringValueFacetCounts} over {@link SortedDocValuesField} and
+ * {@link KeywordField}.
+ */
+public class StringValueFacetCountsExample {
+
+  private final Directory indexDir = new ByteBuffersDirectory();
+  private final FacetsConfig config = new FacetsConfig();
+
+  /** Empty constructor */
+  public StringValueFacetCountsExample() {}
+
+  /** Build the example index. */
+  private void index() throws IOException {
+    IndexWriter indexWriter =
+        new IndexWriter(
+            indexDir, new IndexWriterConfig(new WhitespaceAnalyzer()).setOpenMode(OpenMode.CREATE));
+
+    Document doc = new Document();
+    doc.add(new KeywordField("Author", "Bob", Field.Store.NO));
+    doc.add(new SortedDocValuesField("Publish Year", new BytesRef("2010")));
+    indexWriter.addDocument(config.build(doc));
+
+    doc = new Document();
+    doc.add(new KeywordField("Author", "Lisa", Field.Store.NO));
+    doc.add(new SortedDocValuesField("Publish Year", new BytesRef("2010")));
+    indexWriter.addDocument(config.build(doc));
+
+    doc = new Document();
+    doc.add(new KeywordField("Author", "Lisa", Field.Store.NO));
+    doc.add(new SortedDocValuesField("Publish Year", new BytesRef("2012")));
+    indexWriter.addDocument(config.build(doc));
+
+    doc = new Document();
+    doc.add(new KeywordField("Author", "Susan", Field.Store.NO));
+    doc.add(new SortedDocValuesField("Publish Year", new BytesRef("2012")));
+    indexWriter.addDocument(config.build(doc));
+
+    doc = new Document();
+    doc.add(new KeywordField("Author", "Frank", Field.Store.NO));
+    doc.add(new SortedDocValuesField("Publish Year", new BytesRef("1999")));
+    indexWriter.addDocument(config.build(doc));
+
+    indexWriter.close();
+  }
+
+  /** User runs a query and counts facets. */
+  private List<FacetResult> search() throws IOException {
+    DirectoryReader indexReader = DirectoryReader.open(indexDir);
+    IndexSearcher searcher = new IndexSearcher(indexReader);
+
+    StringDocValuesReaderState authorState = new StringDocValuesReaderState(indexReader, "Author");
+    StringDocValuesReaderState publishState =
+        new StringDocValuesReaderState(indexReader, "Publish Year");
+
+    // Aggregatses the facet counts
+    FacetsCollector fc = new FacetsCollector();
+
+    // MatchAllDocsQuery is for "browsing" (counts facets
+    // for all non-deleted docs in the index); normally
+    // you'd use a "normal" query:
+    FacetsCollector.search(searcher, new MatchAllDocsQuery(), 10, fc);
+
+    // Retrieve results
+    Facets authorFacets = new StringValueFacetCounts(authorState, fc);
+    Facets publishFacets = new StringValueFacetCounts(publishState, fc);
+
+    List<FacetResult> results = new ArrayList<>();
+    results.add(authorFacets.getTopChildren(10, "Author"));
+    results.add(publishFacets.getTopChildren(10, "Publish Year"));
+    indexReader.close();
+
+    return results;
+  }
+
+  /** Runs the search example. */
+  public List<FacetResult> runSearch() throws IOException {
+    index();
+    return search();
+  }
+
+  /** Runs the search and drill-down examples and prints the results. */
+  public static void main(String[] args) throws Exception {
+    System.out.println("Facet counting example:");
+    System.out.println("-----------------------");
+    StringValueFacetCountsExample example = new StringValueFacetCountsExample();
+    List<FacetResult> results = example.runSearch();
+    System.out.println("Author: " + results.get(0));
+    System.out.println("Publish Year: " + results.get(1));
+  }
+}