LUCENE-8050: PerFieldDocValuesFormat should not get the DocValuesFormat on a field that has no doc values.

Closes #1408

lucene/CHANGES.txt

@@ -131,6 +131,9 @@ Improvements
 
 * LUCENE-9279: Update dictionary version for Ukrainian analyzer to 4.9.1 (Andriy Rysin via Dawid Weiss)
 
+* LUCENE-8050: PerFieldDocValuesFormat should not get the DocValuesFormat on a field that has no doc values.
+  (David Smiley, Juan Rodriguez)
+
 Optimizations
 ---------------------
 

lucene/core/src/java/org/apache/lucene/codecs/perfield/PerFieldDocValuesFormat.java

@@ -135,6 +135,9 @@ public abstract class PerFieldDocValuesFormat extends DocValuesFormat {
 
       // Group each consumer by the fields it handles
       for (FieldInfo fi : mergeState.mergeFieldInfos) {
+        if (fi.getDocValuesType() == DocValuesType.NONE) {
+          continue;
+        }
         // merge should ignore current format for the fields being merged
         DocValuesConsumer consumer = getInstance(fi, true);
         Collection<String> fieldsForConsumer = consumersToField.get(consumer);

lucene/core/src/test/org/apache/lucene/codecs/perfield/TestPerFieldDocValuesFormat.java

@@ -36,6 +36,7 @@ import org.apache.lucene.document.BinaryDocValuesField;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.NumericDocValuesField;
+import org.apache.lucene.document.TextField;
 import org.apache.lucene.index.BaseDocValuesFormatTestCase;
 import org.apache.lucene.index.BinaryDocValues;
 import org.apache.lucene.index.DirectoryReader;
@@ -65,7 +66,7 @@ public class TestPerFieldDocValuesFormat extends BaseDocValuesFormatTestCase {
   
   @Override
   public void setUp() throws Exception {
-    codec = new RandomCodec(new Random(random().nextLong()), Collections.<String>emptySet());
+    codec = new RandomCodec(new Random(random().nextLong()), Collections.emptySet());
     super.setUp();
   }
   
@@ -189,6 +190,43 @@ public class TestPerFieldDocValuesFormat extends BaseDocValuesFormatTestCase {
     directory.close();
   }
 
+  public void testDocValuesMergeWithIndexedFields() throws IOException {
+    MergeRecordingDocValueFormatWrapper docValuesFormat = new MergeRecordingDocValueFormatWrapper(TestUtil.getDefaultDocValuesFormat());
+
+    IndexWriterConfig iwc = new IndexWriterConfig();
+    iwc.setCodec(new AssertingCodec() {
+      @Override
+      public DocValuesFormat getDocValuesFormatForField(String field) {
+        return docValuesFormat;
+      }
+    });
+
+    Directory directory = newDirectory();
+
+    IndexWriter iwriter = new IndexWriter(directory, iwc);
+
+    Document doc = new Document();
+    doc.add(new NumericDocValuesField("dv1", 5));
+    doc.add(new TextField("normalField", "not a doc value", Field.Store.NO));
+    iwriter.addDocument(doc);
+    iwriter.commit();
+
+    doc = new Document();
+    doc.add(new TextField("anotherField", "again no doc values here", Field.Store.NO));
+    doc.add(new TextField("normalField", "my document without doc values", Field.Store.NO));
+    iwriter.addDocument(doc);
+    iwriter.commit();
+
+
+    iwriter.forceMerge(1, true);
+    iwriter.close();
+
+    // "normalField" and "anotherField" are ignored when merging doc values.
+    assertEquals(1, docValuesFormat.nbMergeCalls);
+    assertEquals(Collections.singletonList("dv1"), docValuesFormat.fieldNames);
+    directory.close();
+  }
+
   private static final class MergeRecordingDocValueFormatWrapper extends DocValuesFormat {
     private final DocValuesFormat delegate;
     final List<String> fieldNames = new ArrayList<>();