reftable: clear cache on full compaction

The merged table contains handles to open files. A full compaction
causes those files to be closed, and so further lookups would fail
with EBADF.

Change-Id: I7bb74f7228ecc7fec9535b00e56a617a9c18e00e
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileReftableTest.java

@@ -59,6 +59,7 @@ import static org.junit.Assert.fail;
 
 import java.io.File;
 import java.io.IOException;
+import java.security.SecureRandom;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -542,6 +543,43 @@ public class FileReftableTest extends SampleDataRepositoryTestCase {
 		assertEquals(RefUpdate.Result.LOCK_FAILURE, rename.rename());
 	}
 
+	@Test
+	public void compactFully() throws Exception {
+		FileReftableDatabase refDb = (FileReftableDatabase) db.getRefDatabase();
+		PersonIdent person = new PersonIdent("jane", "jane@invalid");
+
+		ObjectId aId  = db.exactRef("refs/heads/a").getObjectId();
+		ObjectId bId  = db.exactRef("refs/heads/b").getObjectId();
+
+		SecureRandom random = new SecureRandom();
+		List<String> strs = new ArrayList<>();
+		for (int i = 0; i < 1024; i++) {
+			strs.add(String.format("%02x",
+					Integer.valueOf(random.nextInt(256))));
+		}
+
+		String randomStr = String.join("", strs);
+		String refName = "branch";
+		for (long i = 0; i < 2; i++) {
+			RefUpdate ru = refDb.newUpdate(refName, false);
+			ru.setNewObjectId(i % 2 == 0 ? aId : bId);
+			ru.setForceUpdate(true);
+			// Only write a large string in the first table, so it becomes much larger
+			// than the second, and the result is not autocompacted.
+			ru.setRefLogMessage(i == 0 ? randomStr : "short", false);
+			ru.setRefLogIdent(person);
+
+			RefUpdate.Result res = ru.update();
+			assertTrue(res == Result.NEW || res == FORCED);
+		}
+
+		assertEquals(refDb.exactRef(refName).getObjectId(), bId);
+		assertTrue(randomStr.equals(refDb.getReflogReader(refName).getReverseEntry(1).getComment()));
+		refDb.compactFully();
+		assertEquals(refDb.exactRef(refName).getObjectId(), bId);
+		assertTrue(randomStr.equals(refDb.getReflogReader(refName).getReverseEntry(1).getComment()));
+	}
+
 	@Test
 	public void reftableRefsStorageClass() throws IOException {
 		Ref b = db.exactRef("refs/heads/b");

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileReftableDatabase.java

@@ -139,6 +139,7 @@ public class FileReftableDatabase extends RefDatabase {
 		reftableDatabase.getLock().lock();
 		try {
 			reftableStack.compactFully();
+			reftableDatabase.clearCache();
 		} finally {
 			reftableDatabase.getLock().unlock();
 		}