Switched to external collection ids for batchGetDocument

src/main/java/io/anserini/search/SimpleSearcher.java

@@ -682,21 +682,20 @@ public Document document(String docid) {
   }
 
   /**
-   * Returns a map of internal Lucene docid to Lucene {@link Document}.
-   * Batch version of {@link #document(int)}.
+   * Returns a map of collection docid to Lucene {@link Document}.
+   * Batch version of {@link #document(String)}.
    *
    * @param docids list of docids
    * @return a map of docid to corresponding Lucene {@link Document}
    */
-  public Map<Integer, Document> batchDocument(List<Integer> docids, int threads){
+  public Map<String, Document> batchGetDocument(List<String> docids, int threads) {
     ThreadPoolExecutor executor = (ThreadPoolExecutor) Executors.newFixedThreadPool(threads);
-    ConcurrentHashMap<Integer, Document> results = new ConcurrentHashMap<>();
+    ConcurrentHashMap<String, Document> results = new ConcurrentHashMap<>();
 
-    for (Integer docid: docids) {
+    for (String docid: docids) {
       executor.execute(() -> {
-        Document result = null;
         try {
-          result = reader.document(docid);
+          Document result = IndexReaderUtils.document(reader, docid);
           results.put(docid, result);
         } catch (Exception e){}
       });

src/test/java/io/anserini/search/SimpleSearcherTest.java

@@ -59,21 +59,17 @@ public void testGetDoc() throws Exception {
   public void testBatchGetDoc() throws Exception {
     SimpleSearcher searcher = new SimpleSearcher(super.tempDir1.toString());
 
-    ArrayList<Integer> ldocIds = new ArrayList<Integer>();
-    ldocIds.add(0);
-    ldocIds.add(1);
-    ldocIds.add(2);
-    ldocIds.add(3);
-
-    Map<Integer, Document> results = searcher.batchDocument(ldocIds, 2);
-
-    assertEquals("here is some text here is some more text. city.",
-            results.get(0).get("contents"));
-    assertEquals("more texts",
-            results.get(1).get("contents"));
-    assertEquals("here is a test",
-            results.get(2).get("contents"));
-    assertNull(results.get(3));
+    ArrayList<String> docIds = new ArrayList<String>();
+    docIds.add("doc1");
+    docIds.add("doc2");
+    docIds.add("doc3");
+    docIds.add("fake_doc");
+
+    Map<String, Document> results = searcher.batchGetDocument(docIds, 2);
+    assertEquals("here is some text here is some more text. city.", results.get("doc1").get("contents"));
+    assertEquals("more texts", results.get("doc2").get("contents"));
+    assertEquals("here is a test", results.get("doc3").get("contents"));
+    assertNull(results.get("fake_doc"));
 
     searcher.close();
   }