Multi-threaded kernel: concurrently running an online backup and updating the…

Multi-threaded kernel: concurrently running an online backup and updating the database resulted in a broken (transactionally incorrect) backup file in some cases.

h2/src/main/org/h2/store/PageStore.java

@@ -196,6 +196,7 @@ public class PageStore implements CacheWriter {
     private int logMode = LOG_MODE_SYNC;
     private boolean lockFile;
     private boolean readMode;
+    private int backupLevel;
 
     /**
      * Create a new page store object.
@@ -412,8 +413,9 @@ public class PageStore implements CacheWriter {
      */
     public synchronized void checkpoint() {
         trace.debug("checkpoint");
-        if (log == null || readMode || database.isReadOnly()) {
-            // the file was never fully opened
+        if (log == null || readMode || database.isReadOnly() || backupLevel > 0) {
+            // the file was never fully opened, or is read-only,
+            // or checkpoint is currently disabled
             return;
         }
         database.checkPowerOff();
@@ -1941,4 +1943,8 @@ public class PageStore implements CacheWriter {
         return systemSession;
     }
 
+    public synchronized void setBackup(boolean start) {
+        backupLevel += start ? 1 : -1;
+    }
+
 }

h2/src/test/org/h2/test/TestBase.java

@@ -412,7 +412,7 @@ public abstract class TestBase {
      * @throws AssertionError always throws an AssertionError
      */
     public void fail() {
-        fail("Unexpected success");
+        fail("Failure");
     }
 
     /**