LUCENE-6523: a new commit, even without user-data changes, is visible to reopened NRT reader

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1683947 13f79535-47bb-0310-9956-ffa450edef68

lucene/CHANGES.txt

@@ -77,6 +77,9 @@ Bug fixes
 * LUCENE-5805: QueryNodeImpl.removeFromParent was doing nothing in a
   costly manner (Christoph Kaser, Cao Manh Dat via Mike McCAndless)
 
+* LUCENE-6523: NRT readers now reflect a new commit even if there is
+  no change to the commit user data (Mike McCandless)
+
 Changes in Runtime Behavior
 
 * LUCENE-6501: The subreader structure in ParallelCompositeReader

lucene/core/src/java/org/apache/lucene/index/IndexWriter.java

@@ -2715,6 +2715,15 @@ public class IndexWriter implements Closeable, TwoPhaseCommit, Accountable {
 
               readerPool.commit(segmentInfos);
 
+              if (changeCount.get() != lastCommitChangeCount) {
+                // There are changes to commit, so we will write a new segments_N in startCommit.
+                // The act of committing is itself an NRT-visible change (an NRT reader that was
+                // just opened before this should see it on reopen) so we increment changeCount
+                // and segments version so a future NRT reopen will see the change:
+                changeCount.incrementAndGet();
+                segmentInfos.changed();
+              }
+
               // Must clone the segmentInfos while we still
               // hold fullFlushLock and while sync'd so that
               // no partial changes (eg a delete w/o

lucene/core/src/test/org/apache/lucene/index/TestIndexWriter.java

@@ -2812,5 +2812,26 @@ public class TestIndexWriter extends LuceneTestCase {
     assertNotNull(r2);
     IOUtils.close(r, r2, w, dir);
   }
+
+  // LUCENE-6523
+  public void testCommitImmediaatelyAfterNRTReopen() throws Exception {
+    Directory dir = newDirectory();
+    IndexWriterConfig iwc = new IndexWriterConfig(new MockAnalyzer(random()));
+    IndexWriter w = new IndexWriter(dir, iwc);
+    w.commit();
+
+    w.addDocument(new Document());
+
+    DirectoryReader r = DirectoryReader.open(w, true);
+    w.commit();
+
+    assertFalse(r.isCurrent());
+
+    DirectoryReader r2 = DirectoryReader.openIfChanged(r);
+    assertNotNull(r2);
+    // segments_N should have changed:
+    assertFalse(r2.getIndexCommit().getSegmentsFileName().equals(r.getIndexCommit().getSegmentsFileName()));
+    IOUtils.close(r, r2, w, dir);
+  }
 }
 

lucene/core/src/test/org/apache/lucene/index/TestIndexWriterReader.java

@@ -103,9 +103,15 @@ public class TestIndexWriterReader extends LuceneTestCase {
     writer.forceMerge(1); // make sure all merging is done etc.
     DirectoryReader reader = writer.getReader();
     writer.commit(); // no changes that are not visible to the reader
+
+    // A commit is now seen as a change to an NRT reader:
+    assertFalse(reader.isCurrent());
+    reader.close();
+    reader = writer.getReader();
     assertTrue(reader.isCurrent());
     writer.close();
-    assertTrue(reader.isCurrent()); // all changes are visible to the reader
+
+    assertTrue(reader.isCurrent());
     iwc = newIndexWriterConfig(new MockAnalyzer(random()));
     writer = new IndexWriter(dir1, iwc);
     assertTrue(reader.isCurrent());
@@ -160,11 +166,12 @@ public class TestIndexWriterReader extends LuceneTestCase {
     r1.close();
     assertTrue(r2.isCurrent());
     writer.close();
-    assertTrue(r2.isCurrent());
+    // writer.close wrote a new commit
+    assertFalse(r2.isCurrent());
     
     DirectoryReader r3 = DirectoryReader.open(dir1);
     assertTrue(r3.isCurrent());
-    assertTrue(r2.isCurrent());
+    assertFalse(r2.isCurrent());
     assertEquals(0, count(new Term("id", id10), r3));
     assertEquals(1, count(new Term("id", Integer.toString(8000)), r3));
 
@@ -172,7 +179,7 @@ public class TestIndexWriterReader extends LuceneTestCase {
     Document doc = new Document();
     doc.add(newTextField("field", "a b c", Field.Store.NO));
     writer.addDocument(doc);
-    assertTrue(r2.isCurrent());
+    assertFalse(r2.isCurrent());
     assertTrue(r3.isCurrent());
 
     writer.close();
@@ -216,7 +223,7 @@ public class TestIndexWriterReader extends LuceneTestCase {
     assertEquals(2, nrtReader.maxDoc()); // sees the actual document added
     assertEquals(1, dirReader.maxDoc());
     writer.close(); // close is actually a commit both should see the changes
-    assertTrue(nrtReader.isCurrent()); 
+    assertFalse(nrtReader.isCurrent()); 
     assertFalse(dirReader.isCurrent()); // this reader has been opened before the writer was closed / committed
     
     dirReader.close();
@@ -259,7 +266,9 @@ public class TestIndexWriterReader extends LuceneTestCase {
     assertTrue(r1.isCurrent());
 
     writer.commit();
-    assertTrue(r1.isCurrent()); // we have seen all changes - no change after opening the NRT reader
+
+    // A commit is seen as a change to NRT reader:
+    assertFalse(r1.isCurrent());
 
     assertEquals(200, r1.maxDoc());