MVStore: simpler API

h2/src/docsrc/html/changelog.html

@@ -23,6 +23,7 @@ Change Log
 </li><li>Issue 73: MySQL compatibility: support REPLACE, patch by Cemo Koc.
 </li><li>The spatial index now works in MVCC mode when using the MVStore storage.
 </li><li>MVStore: concurrency problems have been fixed.
+    The API has been simplified.
 </li><li>Improve error message when dropping an index that belongs to a constraint,
     specify constraint in error message.
 </li><li>Issue 518: java.sql.Connection.commit() freezes after LOB modification with EXCLUSIVE connection

h2/src/main/org/h2/mvstore/MVStore.java

@@ -59,7 +59,7 @@ TransactionStore:
 MVStore:
 - automated 'kill process' and 'power failure' test
 - update checkstyle
-- auto-compact from time to time and on close
+- feature to auto-compact from time to time and on close
 - test and possibly improve compact operation (for large dbs)
 - possibly split chunk metadata into immutable and mutable
 - compact: avoid processing pages using a counting bloom filter
@@ -115,6 +115,19 @@ MVStore:
 - support log structured merge style operations (blind writes)
     using one map per level plus bloom filter
 - have a strict call order MVStore -> MVMap -> Page -> FileStore
+- autocommit mode (default) and manual mode
+- manual mode: combine commit and store;
+    rollback only to chunk
+- rename writeDelay to commitDelay, default 1 s
+- rollback() to rollback to the latest commit; throws exception
+    in autocommit mode
+- fix documentation (including examples)
+- autocommit commits, stores, and compacts from time to time;
+    the background thread should wait at least 90% of the
+    configured write delay to store changes 
+- currently, uncommitted changes are stored if there are many transient changes,
+    and rolled back when opening - is this really needed?
+- compact* should also store uncommitted changes (if there are any)
 
 */
 
@@ -141,6 +154,7 @@ public class MVStore {
      * The background thread, if any.
      */
     volatile Thread backgroundThread;
+    final Object backgroundThreadSync = new Object();
 
     private volatile boolean reuseSpace = true;
 
@@ -176,9 +190,9 @@ public class MVStore {
             new ConcurrentHashMap<Long, HashMap<Integer, Chunk>>();
 
     /**
-     * The metadata map.
+     * The metadata map. Write access to this map needs to be synchronized on the store.
      */
-    private MVMapConcurrent<String, String> meta;
+    private MVMap<String, String> meta;
 
     private final ConcurrentHashMap<Integer, MVMap<?, ?>> maps =
             new ConcurrentHashMap<Integer, MVMap<?, ?>>();
@@ -208,6 +222,12 @@ public class MVStore {
      */
     private long lastStoredVersion;
 
+    /**
+     * The estimated number of unsaved pages
+     * (this number may not be completely accurate,
+     * because it may be changed concurrently, and
+     * because temporary pages are counted)
+     */
     private int unsavedPageCount;
     private int unsavedPageCountMax;
     private boolean storeNeeded;
@@ -220,11 +240,6 @@ public class MVStore {
 
     private long lastStoreTime;
 
-    /**
-     * To which version to roll back when opening the store after a crash.
-     */
-    private long lastCommittedVersion;
-
     /**
      * The earliest chunk to retain, if any.
      */
@@ -234,6 +249,8 @@ public class MVStore {
      * The version of the current store operation (if any).
      */
     private volatile long currentStoreVersion = -1;
+    
+    private Thread currentStoreThread;
 
     private volatile boolean metaChanged;
 
@@ -256,7 +273,7 @@ public class MVStore {
         pageSplitSize = o == null ? 6 * 1024 : (Integer) o;
         o = config.get("backgroundExceptionHandler");
         this.backgroundExceptionHandler = (UncaughtExceptionHandler) o;
-        meta = new MVMapConcurrent<String, String>(StringDataType.INSTANCE, StringDataType.INSTANCE);
+        meta = new MVMap<String, String>(StringDataType.INSTANCE, StringDataType.INSTANCE);
         HashMap<String, String> c = New.hashMap();
         c.put("id", "0");
         c.put("createVersion", Long.toString(currentVersion));
@@ -320,10 +337,6 @@ public class MVStore {
                     readMeta();
                 }
             }
-            long rollback = DataUtils.parseLong(meta.get("rollbackOnOpen"), -1);
-            if (rollback != -1) {
-                rollbackTo(rollback);
-            }
         } catch (IllegalStateException e) {
             try {
                 closeStore(false);
@@ -337,7 +350,6 @@ public class MVStore {
             }
         }
         lastStoreTime = getTime();
-        this.lastCommittedVersion = currentVersion;
 
         // setWriteDelay starts the thread, but only if
         // the parameter is different than the current value
@@ -403,7 +415,7 @@ public class MVStore {
      * @param builder the map builder
      * @return the map
      */
-    public <M extends MVMap<K, V>, K, V> M openMap(String name, MVMap.MapBuilder<M, K, V> builder) {
+    public synchronized <M extends MVMap<K, V>, K, V> M openMap(String name, MVMap.MapBuilder<M, K, V> builder) {
         checkOpen();
         String x = meta.get("name." + name);
         int id;
@@ -445,17 +457,17 @@ public class MVStore {
      * Get the metadata map. This data is for informational purposes only. The
      * data is subject to change in future versions.
      * <p>
-     * The data should not be modified (doing so may corrupt the store). Writing
-     * to it is not always detected as a modification, so that changes to it
-     * might not be stored.
+     * The data in this map should not be modified (changing system data may
+     * corrupt the store). If modifications are needed, they need be
+     * synchronized on the store.
      * <p>
-     * It contains the following entries:
-     * 
+     * The metadata map contains the following entries:
      * <pre>
+     * chunk.{chunkId} = {chunk metadata}
      * name.{name} = {mapId}
      * map.{mapId} = {map metadata}
      * root.{mapId} = {root position}
-     * chunk.{chunkId} = {chunk metadata}
+     * setting.storeVersion = {version}
      * </pre>
      * 
      * @return the metadata map
@@ -636,9 +648,8 @@ public class MVStore {
     }
 
     /**
-     * Close the file and the store. If there are any committed but unsaved
-     * changes, they are written to disk first. If any temporary data was
-     * written but not committed, this is rolled back. All open maps are closed.
+     * Close the file and the store. If there are any uncommitted changes, they
+     * are written to disk first. All open maps are closed.
      * <p>
      * It is not allowed to concurrently call close and store.
      */
@@ -648,18 +659,8 @@ public class MVStore {
         }
         if (fileStore != null && !fileStore.isReadOnly()) {
             stopBackgroundThread();
-
-            if (currentStoreVersion >= 0) {
-                // in this case, store is called manually in another thread
-                throw DataUtils.newIllegalStateException(
-                        DataUtils.ERROR_WRITING_FAILED,
-                        "Can not close while storing");
-            }
-
-            if (hasUnsavedChanges() || lastCommittedVersion != currentVersion) {
-                rollbackTo(lastCommittedVersion);
-                metaChanged = true;
-                store(false);
+            if (hasUnsavedChanges()) {
+                store();
             }
         }
         closeStore(true);
@@ -739,17 +740,6 @@ public class MVStore {
         return c;
     }
 
-    /**
-     * Increment the current version, without committing the changes.
-     *
-     * @return the new version
-     */
-    public long incrementVersion() {
-        long v = ++currentVersion;
-        setWriteVersion(v);
-        return v;
-    }
-
     private void setWriteVersion(long version) {
         for (MVMap<?, ?> map : maps.values()) {
             map.setWriteVersion(version);
@@ -768,11 +758,11 @@ public class MVStore {
      * @return the new version
      */
     public long commit() {
-        long v = incrementVersion();
-        lastCommittedVersion = v;
-        if (writeDelay == 0) {
-            store(false);
+        if (fileStore != null) {
+            return store();
         }
+        long v = ++currentVersion;
+        setWriteVersion(v);
         return v;
     }
 
@@ -781,29 +771,17 @@ public class MVStore {
      * there are no unsaved changes, otherwise it increments the current version
      * and stores the data (for file based stores).
      * <p>
-     * One store operation may run at any time.
+     * At most one store operation may run at any time.
      *
      * @return the new version (incremented if there were changes)
      */
-    public long store() {
-        checkOpen();
-        return store(false);
-    }
-
-    /**
-     * Store changes. Changes that are marked as temporary are rolled back after
-     * a restart.
-     *
-     * @param temp whether the changes are only temporary (not committed), and
-     *        should be rolled back after a crash
-     * @return the new version (incremented if there were changes)
-     */
-    private synchronized long store(boolean temp) {
+    public synchronized long store() {
         if (closed) {
             return currentVersion;
         }
         if (fileStore == null) {
-            return incrementVersion();
+            throw DataUtils.newIllegalStateException(
+                    DataUtils.ERROR_WRITING_FAILED, "This is an in-memory store");
         }
         if (currentStoreVersion >= 0) {
             // store is possibly called within store, if the meta map changed
@@ -818,37 +796,24 @@ public class MVStore {
         }
         try {
             currentStoreVersion = currentVersion;
-            return storeNow(temp);
+            currentStoreThread = Thread.currentThread();
+            return storeNow();
         } finally {
             // in any case reset the current store version,
             // to allow closing the store
             currentStoreVersion = -1;
+            currentStoreThread = null;
         }
     }
 
-    private long storeNow(boolean temp) {
+    private long storeNow() {
         int currentUnsavedPageCount = unsavedPageCount;
         long storeVersion = currentStoreVersion;
         long version = ++currentVersion;
+        setWriteVersion(version);
         long time = getTime();
         lastStoreTime = time;
-        if (temp) {
-            meta.put("rollbackOnOpen", Long.toString(lastCommittedVersion));
-            // find the oldest chunk to retain
-            long minVersion = Long.MAX_VALUE;
-            Chunk minChunk = null;
-            for (Chunk c : chunks.values()) {
-                if (c.version < minVersion) {
-                    minVersion = c.version;
-                    minChunk = c;
-                }
-            }
-            retainChunk = minChunk;
-        } else {
-            lastCommittedVersion = version;
-            meta.remove("rollbackOnOpen");
-            retainChunk = null;
-        }
+        retainChunk = null;
 
         // the last chunk was not completely correct in the last store()
         // this needs to be updated now (it's better not to update right after
@@ -983,10 +948,9 @@ public class MVStore {
         // some pages might have been changed in the meantime (in the newest version)
         unsavedPageCount = Math.max(0, unsavedPageCount - currentUnsavedPageCount);
 
-        if (!temp) {
-            metaChanged = false;
-            lastStoredVersion = storeVersion;
-        }
+        metaChanged = false;
+        lastStoredVersion = storeVersion;
+
         return version;
     }
 
@@ -1053,7 +1017,7 @@ public class MVStore {
                 if (v > storeVersion) {
                     continue;
                 }
-                Map<Integer, Chunk> freed = e.getValue();
+                HashMap<Integer, Chunk> freed = e.getValue();
                 for (Chunk f : freed.values()) {
                     Chunk c = chunks.get(f.id);
                     if (c == null) {
@@ -1146,6 +1110,9 @@ public class MVStore {
      * @return if there are any changes
      */
     public boolean hasUnsavedChanges() {
+        ;
+        // TODO maybe private; rename to hasUncommittedChanges
+        
         checkOpen();
         if (metaChanged) {
             return true;
@@ -1281,7 +1248,7 @@ public class MVStore {
     }
 
     /**
-     * Force all changes to be written to the storage. The default
+     * Force all stored changes to be written to the storage. The default
      * implementation calls FileChannel.force(true).
      */
     public void sync() {
@@ -1484,11 +1451,13 @@ public class MVStore {
         Chunk c = getChunk(pos);
         long version = currentVersion;
         if (map == meta && currentStoreVersion >= 0) {
-            // if the meta map is modified while storing,
-            // then this freed page needs to be registered
-            // with the stored chunk, so that the old chunk
-            // can be re-used
-            version = currentStoreVersion;
+            if (Thread.currentThread() == currentStoreThread) {
+                // if the meta map is modified while storing,
+                // then this freed page needs to be registered
+                // with the stored chunk, so that the old chunk
+                // can be re-used
+                version = currentStoreVersion;
+            }
         }
         registerFreePage(version, c.id, DataUtils.getPageMaxLength(pos), 1);
     }
@@ -1663,10 +1632,9 @@ public class MVStore {
     }
 
     /**
-     * Get the maximum number of unsaved pages. If this number is exceeded,
-     * the unsaved changes are stored to disk, including uncommitted changes.
-     * Saved uncommitted changes are rolled back when opening the store.
-     *
+     * Get the maximum number of unsaved pages. If this number is exceeded, the
+     * unsaved changes are stored to disk.
+     * 
      * @return the number of maximum unsaved pages
      */
     public int getUnsavedPageCountMax() {
@@ -1677,8 +1645,8 @@ public class MVStore {
      * Increment the number of unsaved pages.
      */
     void registerUnsavedPage() {
-        unsavedPageCount++;
-        if (unsavedPageCount > unsavedPageCountMax && unsavedPageCountMax > 0) {
+        int count = ++unsavedPageCount;
+        if (count > unsavedPageCountMax && unsavedPageCountMax > 0) {
             storeNeeded = true;
         }
     }
@@ -1689,7 +1657,7 @@ public class MVStore {
     void beforeWrite() {
         if (storeNeeded) {
             storeNeeded = false;
-            store(true);
+            store();
         }
     }
 
@@ -1711,11 +1679,21 @@ public class MVStore {
      *
      * @param version the new store version
      */
-    public void setStoreVersion(int version) {
+    public synchronized void setStoreVersion(int version) {
         checkOpen();
         markMetaChanged();
         meta.put("setting.storeVersion", Integer.toString(version));
     }
+    
+    /**
+     * Revert to the beginning of the current version.
+     */
+    public void rollback() {
+        ;
+        // TODO document and test
+        
+        rollbackTo(currentVersion);
+    }
 
     /**
      * Revert to the beginning of the given version. All later changes (stored
@@ -1741,7 +1719,6 @@ public class MVStore {
             freedPageSpace.clear();
             currentVersion = version;
             setWriteVersion(version);
-            lastCommittedVersion = version;
             metaChanged = false;
             return;
         }
@@ -1816,12 +1793,10 @@ public class MVStore {
         // rollback might have rolled back the stored chunk metadata as well
         Chunk c = chunks.get(lastChunkId - 1);
         if (c != null) {
-            markMetaChanged();
             meta.put("chunk." + c.id, c.asString());
         }
         currentVersion = version;
         setWriteVersion(version);
-        lastCommittedVersion = version;
     }
 
     private void revertTemp(long storeVersion) {
@@ -1847,15 +1822,6 @@ public class MVStore {
         return currentVersion;
     }
 
-    /**
-     * Get the last committed version.
-     *
-     * @return the version
-     */
-    public long getCommittedVersion() {
-        return lastCommittedVersion;
-    }
-
     /**
      * Get the file store.
      *
@@ -1889,7 +1855,7 @@ public class MVStore {
      * @param map the map
      * @param newName the new name
      */
-    public void renameMap(MVMap<?, ?> map, String newName) {
+    public synchronized void renameMap(MVMap<?, ?> map, String newName) {
         checkOpen();
         DataUtils.checkArgument(map != meta,
                 "Renaming the meta map is not allowed");
@@ -1912,7 +1878,7 @@ public class MVStore {
      *
      * @param map the map
      */
-    public void removeMap(MVMap<?, ?> map) {
+    public synchronized void removeMap(MVMap<?, ?> map) {
         checkOpen();
         DataUtils.checkArgument(map != meta,
                 "Removing the meta map is not allowed");
@@ -1932,7 +1898,7 @@ public class MVStore {
      * @param id the map id
      * @return the name
      */
-    String getMapName(int id) {
+    synchronized String getMapName(int id) {
         String m = meta.get("map." + id);
         return DataUtils.parseMap(m).get("name");
     }
@@ -1941,14 +1907,13 @@ public class MVStore {
      * Store all unsaved changes, if there are any that are committed.
      */
     void storeInBackground() {
-        if (closed || unsavedPageCount == 0) {
+        if (unsavedPageCount == 0 || closed) {
             return;
         }
+
         // could also store when there are many unsaved pages,
         // but according to a test it doesn't really help
-        if (lastStoredVersion >= lastCommittedVersion) {
-            return;
-        }
+        
         long time = getTime();
         if (time <= lastStoreTime + writeDelay) {
             return;
@@ -1957,7 +1922,7 @@ public class MVStore {
             return;
         }
         try {
-            store(true);
+            store();
         } catch (Exception e) {
             if (backgroundExceptionHandler != null) {
                 backgroundExceptionHandler.uncaughtException(null, e);
@@ -1981,13 +1946,13 @@ public class MVStore {
     }
 
     private void stopBackgroundThread() {
-        if (backgroundThread == null) {
+        Thread t = backgroundThread;
+        if (t == null) {
             return;
         }
-        Thread t = backgroundThread;
         backgroundThread = null;
-        synchronized (this) {
-            notify();
+        synchronized (backgroundThreadSync) {
+            backgroundThreadSync.notifyAll();
         }
         try {
             t.join();
@@ -1997,13 +1962,12 @@ public class MVStore {
     }
 
     /**
-     * Set the maximum delay in milliseconds to store committed changes (for
-     * file-based stores).
+     * Set the maximum delay in milliseconds to commit changes.
      * <p>
-     * The default is 1000, meaning committed changes are stored after at
+     * The default is 1000, meaning changes are committed after at
      * most one second.
      * <p>
-     * When the value is set to -1, committed changes are only written when
+     * When the value is set to -1, changes are only written when
      * calling the store method. When the value is set to 0, committed
      * changes are immediately written on a commit, but please note this
      * decreases performance and does still not guarantee the disk will
@@ -2012,6 +1976,8 @@ public class MVStore {
      * @param millis the maximum delay
      */
     public void setWriteDelay(int millis) {
+        ; 
+        // TODO rename to commitDelay
         if (writeDelay == millis) {
             return;
         }
@@ -2050,12 +2016,17 @@ public class MVStore {
 
         @Override
         public void run() {
-            while (store.backgroundThread != null) {
-                synchronized (store) {
+            while (true) {
+                Thread t = store.backgroundThread;
+                if (t == null) {
+                    break;
+                }
+                Object sync = store.backgroundThreadSync;
+                synchronized (sync) {
                     try {
-                        store.wait(sleep);
+                        sync.wait(sleep);
                     } catch (InterruptedException e) {
-                        // ignore
+                        continue;
                     }
                 }
                 store.storeInBackground();
@@ -2145,9 +2116,8 @@ public class MVStore {
 
         /**
          * Set the size of the write buffer, in MB (for file-based stores).
-         * Changes are automatically stored if the buffer grows larger than
-         * this. However, unless the changes are committed later on, they are
-         * rolled back when opening the store.
+         * Unless auto-commit is disabled, changes are automatically stored if
+         * the buffer grows larger than this.
          * <p>
          * The default is 4 MB.
          * <p>

h2/src/main/org/h2/mvstore/OffHeapStore.java

@@ -121,8 +121,7 @@ public class OffHeapStore extends FileStore {
 
     @Override
     public void close() {
-        truncate(0);
-        freeSpace.clear();
+        // do nothing (keep the data until it is garbage collected)
     }
 
     @Override

h2/src/main/org/h2/mvstore/db/MVTableEngine.java

@@ -260,7 +260,7 @@ public class MVTableEngine implements TableEngine {
         public void compactFile(long maxCompactTime) {
             store.setRetentionTime(0);
             long start = System.currentTimeMillis();
-            while (store.compact(90)) {
+            while (store.compact(99)) {
                 store.sync();
                 long time = System.currentTimeMillis() - start;
                 if (time > maxCompactTime) {
@@ -280,7 +280,7 @@ public class MVTableEngine implements TableEngine {
         public void close(long maxCompactTime) {
             if (!store.isClosed() && store.getFileStore() != null) {
                 if (!store.getFileStore().isReadOnly()) {
-                    store.store();
+                    transactionStore.close();
                     long start = System.currentTimeMillis();
                     while (store.compact(90)) {
                         long time = System.currentTimeMillis() - start;

h2/src/main/org/h2/mvstore/db/TransactionStore.java

@@ -170,7 +170,9 @@ public class TransactionStore {
     public synchronized void close() {
         // to avoid losing transaction ids
         settings.put(LAST_TRANSACTION_ID, "" + lastTransactionId);
-        store.store();
+        if (store.getFileStore() != null) {
+            store.store();
+        }
     }
 
     /**
@@ -191,7 +193,6 @@ public class TransactionStore {
     private void commitIfNeeded() {
         if (store.getUnsavedPageCount() > MAX_UNSAVED_PAGES) {
             if (store.getFileStore() != null) {
-                store.commit();
                 store.store();
             }
         }
@@ -354,10 +355,10 @@ public class TransactionStore {
             firstOpenTransaction = -1;
         }
         if (store.getWriteDelay() == 0) {
-            if (store.getFileStore() == null) {
-                return;
+            if (store.getFileStore() != null) {
+                store.store();
             }
-            store.commit();
+            return;
         }
         // to avoid having to store the transaction log,
         // if there is no open transaction,
@@ -1207,7 +1208,7 @@ public class TransactionStore {
          */
         public Iterator<K> keyIterator(K from, boolean includeUncommitted) {
             Cursor<K> it = map.keyIterator(from);
-            return wrapIterator(it, false);
+            return wrapIterator(it, includeUncommitted);
         }
 
         /**

h2/src/test/org/h2/test/TestAll.java

@@ -470,18 +470,18 @@ kill -9 `jps -l | grep "org.h2.test." | cut -d " " -f 1`
             prof.interval = 1;
             prof.startCollecting();
             if (test.mvStore) {
-                TestPerformance.main("-init", "-db", "9", "-size", "10000");
+                TestPerformance.main("-init", "-db", "9", "-size", "1000");
             } else {
                 TestPerformance.main("-init", "-db", "1");
             }
             prof.stopCollecting();
-            System.out.println(prof.getTop(3));
+            System.out.println(prof.getTop(30));
             if (test.mvStore) {
                 prof = new Profiler();
                 prof.depth = 16;
                 prof.interval = 1;
                 prof.startCollecting();
-                TestPerformance.main("-init", "-db", "1", "-size", "10000");
+                TestPerformance.main("-init", "-db", "1", "-size", "1000");
                 prof.stopCollecting();
                 System.out.println(prof.getTop(3));
             }

h2/src/test/org/h2/test/store/TestConcurrent.java

@@ -43,7 +43,6 @@ public class TestConcurrent extends TestMVStore {
 
     @Override
     public void test() throws Exception {
-        
         FileUtils.deleteRecursive(getBaseDir(), true);
         FileUtils.createDirectories(getBaseDir());
         FileUtils.deleteRecursive("memFS:", false);
@@ -110,7 +109,7 @@ public class TestConcurrent extends TestMVStore {
                 m.clear();
                 s.removeMap(m);
                 if (x % 5 == 0) {
-                    s.incrementVersion();
+                    s.commit();
                 }
             }
             task.get();
@@ -124,9 +123,9 @@ public class TestConcurrent extends TestMVStore {
                 }
             }
             assertEquals(1, chunkCount);
-            
             s.close();
         }
+        FileUtils.deleteRecursive("memFS:", false);
     }
 
     private void testConcurrentStoreAndRemoveMap() throws InterruptedException {
@@ -159,6 +158,7 @@ public class TestConcurrent extends TestMVStore {
         }
         task.get();
         s.close();
+        FileUtils.deleteRecursive("memFS:", false);
     }
 
     private void testConcurrentStoreAndClose() throws InterruptedException {
@@ -200,6 +200,7 @@ public class TestConcurrent extends TestMVStore {
             }
             s.close();
         }
+        FileUtils.deleteRecursive("memFS:", false);
     }
 
     /**
@@ -249,7 +250,7 @@ public class TestConcurrent extends TestMVStore {
                 }
                 m.get(rand.nextInt(size));
             }
-            s.incrementVersion();
+            s.commit();
             Thread.sleep(1);
         }
         task.get();
@@ -341,7 +342,7 @@ public class TestConcurrent extends TestMVStore {
         for (int k = 0; k < 10000; k++) {
             Iterator<Integer> it = map.keyIterator(r.nextInt(len));
             long old = s.getCurrentVersion();
-            s.incrementVersion();
+            s.commit();
             s.setRetainVersion(old - 100);
             while (map.getVersion() == old) {
                 Thread.yield();
@@ -423,7 +424,7 @@ public class TestConcurrent extends TestMVStore {
                     notDetected.incrementAndGet();
                 }
             }
-            s.incrementVersion();
+            s.commit();
             Thread.sleep(1);
         }
         task.get();
@@ -438,7 +439,7 @@ public class TestConcurrent extends TestMVStore {
         for (int i = 0; i < size; i++) {
             m.put(i, x);
         }
-        s.incrementVersion();
+        s.commit();
         Task task = new Task() {
             @Override
             public void call() throws Exception {
@@ -462,7 +463,7 @@ public class TestConcurrent extends TestMVStore {
             for (int i = 0; i < size; i++) {
                 m.put(i, x);
             }
-            s.incrementVersion();
+            s.commit();
             Thread.sleep(1);
         }
         task.get();

h2/src/test/org/h2/test/store/TestMVStore.java

@@ -148,7 +148,7 @@ public class TestMVStore extends TestBase {
             s.store();
         }
         assertTrue(1000 < offHeap.getWriteCount());
-        // s.close();
+        s.close();
 
         s = new MVStore.Builder().
                 fileStore(offHeap).
@@ -253,7 +253,6 @@ public class TestMVStore extends TestBase {
         m = s.openMap("data");
         s.getFileStore().getFile().close();
         m.put(1, "Hello");
-        s.commit();
         for (int i = 0; i < 100; i++) {
             if (exRef.get() != null) {
                 break;
@@ -330,19 +329,19 @@ public class TestMVStore extends TestBase {
                 fileName(fileName).
                 open();
         m = s.openMap("data");
-        assertFalse(m.containsKey(1));
+        assertTrue(m.containsKey(1));
 
-        m.put(1, data);
-        s.commit();
-        m.put(2, data);
+        m.put(-1, data);
+        s.store();
+        m.put(-2, data);
         s.close();
 
         s = new MVStore.Builder().
                 fileName(fileName).
                 open();
         m = s.openMap("data");
-        assertTrue(m.containsKey(1));
-        assertFalse(m.containsKey(2));
+        assertTrue(m.containsKey(-1));
+        assertTrue(m.containsKey(-2));
 
         s.close();
         FileUtils.delete(fileName);
@@ -377,7 +376,7 @@ public class TestMVStore extends TestBase {
         m.put(1, "Hello");
         s.store();
         long v = s.getCurrentVersion();
-        m.put(2, "World");
+        m.put(2, "World.");
         Thread.sleep(5);
         // must not store, as nothing has been committed yet
         s.closeImmediately();
@@ -386,9 +385,11 @@ public class TestMVStore extends TestBase {
                 open();
         s.setWriteDelay(1);
         m = s.openMap("data");
-        assertEquals(null, m.get(2));
+        assertEquals("World.", m.get(2));
         m.put(2, "World");
         s.commit();
+        s.store();
+        v = s.getCurrentVersion();
         m.put(3, "!");
 
         for (int i = 100; i > 0; i--) {
@@ -400,7 +401,7 @@ public class TestMVStore extends TestBase {
             }
             Thread.sleep(1);
         }
-        s.close();
+        s.closeImmediately();
 
         s = new MVStore.Builder().
                 fileName(fileName).
@@ -408,7 +409,7 @@ public class TestMVStore extends TestBase {
         m = s.openMap("data");
         assertEquals("Hello", m.get(1));
         assertEquals("World", m.get(2));
-        assertFalse(m.containsKey(3));
+        assertEquals("!", m.get(3));
         s.close();
 
         FileUtils.delete(fileName);
@@ -517,7 +518,7 @@ public class TestMVStore extends TestBase {
         MVMap<Integer, Integer> map;
         map = s.openMap("hello");
         map.put(1, 10);
-        long old = s.incrementVersion();
+        long old = s.commit();
         s.renameMap(map, "world");
         map.put(2, 20);
         assertEquals("world", map.getName());
@@ -557,7 +558,7 @@ public class TestMVStore extends TestBase {
         s.store();
         s.close();
         int[] expectedReadsForCacheSize = {
-                3405, 2590, 1924, 1440, 1103, 956, 918
+                3405, 2590, 1924, 1440, 1108, 956, 918
         };
         for (int cacheSize = 0; cacheSize <= 6; cacheSize += 4) {
             s = new MVStore.Builder().
@@ -816,8 +817,10 @@ public class TestMVStore extends TestBase {
         MVStore s = MVStore.open(fileName);
         assertEquals(0, s.getCurrentVersion());
         assertEquals(0, s.getStoreVersion());
+        s.setStoreVersion(0);
+        s.store();
         s.setStoreVersion(1);
-        s.close();
+        s.closeImmediately();
         s = MVStore.open(fileName);
         assertEquals(1, s.getCurrentVersion());
         assertEquals(0, s.getStoreVersion());
@@ -840,7 +843,7 @@ public class TestMVStore extends TestBase {
             map.put(i, 10 * i);
         }
         Iterator<Integer> it = map.keySet().iterator();
-        s.incrementVersion();
+        s.commit();
         for (int i = 0; i < len; i += 2) {
             map.remove(i);
         }
@@ -916,7 +919,7 @@ public class TestMVStore extends TestBase {
         long oldVersion = s.getCurrentVersion();
 
         // from now on, the old version is read-only
-        s.incrementVersion();
+        s.commit();
 
         // more changes, in the new version
         // changes can be rolled back if required
@@ -976,7 +979,7 @@ public class TestMVStore extends TestBase {
                     if (op == 1) {
                         m.put("1", "" + s.getCurrentVersion());
                     }
-                    s.incrementVersion();
+                    s.commit();
                 }
                 for (int j = 0; j < s.getCurrentVersion(); j++) {
                     MVMap<String, String> old = m.openVersion(j);
@@ -997,14 +1000,14 @@ public class TestMVStore extends TestBase {
         MVMap<String, String> m;
         m = s.openMap("data");
         long first = s.getCurrentVersion();
-        s.incrementVersion();
+        s.commit();
         m.put("1", "Hello");
         m.put("2", "World");
         for (int i = 10; i < 20; i++) {
             m.put("" + i, "data");
         }
         long old = s.getCurrentVersion();
-        s.incrementVersion();
+        s.commit();
         m.put("1", "Hallo");
         m.put("2", "Welt");
         MVMap<String, String> mFirst;
@@ -1119,7 +1122,7 @@ public class TestMVStore extends TestBase {
         assertTrue(s.hasUnsavedChanges());
         MVMap<String, String> m0 = s.openMap("data0");
         m.put("1", "Hello");
-        assertEquals(1, s.incrementVersion());
+        assertEquals(1, s.commit());
         s.rollbackTo(1);
         assertEquals(1, s.getCurrentVersion());
         assertEquals("Hello", m.get("1"));
@@ -1167,16 +1170,13 @@ public class TestMVStore extends TestBase {
         assertEquals("Hello", m.get("1"));
         assertFalse(m0.isReadOnly());
         m.put("1",  "Hallo");
-        s.incrementVersion();
+        s.commit();
         long v3 = s.getCurrentVersion();
         assertEquals(3, v3);
-        long v4 = s.store();
-        assertEquals(4, v4);
-        assertEquals(4, s.getCurrentVersion());
         s.close();
 
         s = openStore(fileName);
-        assertEquals(4, s.getCurrentVersion());
+        assertEquals(3, s.getCurrentVersion());
         m = s.openMap("data");
         m.put("1",  "Hi");
         s.store();
@@ -1185,7 +1185,7 @@ public class TestMVStore extends TestBase {
         s = openStore(fileName);
         m = s.openMap("data");
         assertEquals("Hi", m.get("1"));
-        s.rollbackTo(v4);
+        s.rollbackTo(v3);
         assertEquals("Hallo", m.get("1"));
         s.close();
 
@@ -1212,7 +1212,7 @@ public class TestMVStore extends TestBase {
         for (int i = 0; i < 10; i++) {
             m2.put("" + i, "Test");
         }
-        long v1 = s.incrementVersion();
+        long v1 = s.commit();
         assertEquals(1, v1);
         assertEquals(1, s.getCurrentVersion());
         MVMap<String, String> m1 = s.openMap("data1");

h2/src/test/org/h2/test/store/TestMVStoreBenchmark.java

@@ -73,7 +73,7 @@ public class TestMVStoreBenchmark extends TestBase {
 
     }
 
-    private static long[] getMemoryUsed(int count, int size) {
+    private long[] getMemoryUsed(int count, int size) {
         long hash, tree, mv;
         ArrayList<Map<Integer, String>> mapList;
         long mem;
@@ -107,6 +107,10 @@ public class TestMVStoreBenchmark extends TestBase {
         mv = getMemory() - mem;
         mapList.size();
 
+        trace("hash: " + hash / 1024 / 1024 + " mb");
+        trace("tree: " + tree / 1024 / 1024 + " mb");
+        trace("mv: " + mv / 1024 / 1024 + " mb");
+
         return new long[]{hash, tree, mv};
     }
 
@@ -179,7 +183,7 @@ public class TestMVStoreBenchmark extends TestBase {
             }
             time = System.currentTimeMillis() - time;
         }
-        // System.out.println(map.getClass().getName() + ": " + time);
+        trace(map.getClass().getName() + ": " + time);
         return time;
     }
 

h2/src/test/org/h2/test/store/TestMVTableEngine.java

@@ -141,7 +141,7 @@ public class TestMVTableEngine extends TestBase {
         conn.close();
         long sizeNew = FileUtils.size(getBaseDir() + "/mvstore"
                 + Constants.SUFFIX_MV_FILE);
-        assertTrue(sizeNew < sizeOld);
+        assertTrue("new: " + sizeNew + " old: " + sizeOld, sizeNew < sizeOld);
     }
 
     private void testTwoPhaseCommit() throws Exception {

h2/src/test/org/h2/test/store/TestTransactionStore.java

@@ -59,6 +59,7 @@ public class TestTransactionStore extends TestBase {
     private void testStopWhileCommitting() throws Exception {
         String fileName = getBaseDir() + "/testStopWhileCommitting.h3";
         FileUtils.delete(fileName);
+        Random r = new Random(0);
 
         for (int i = 0; i < 10;) {
             MVStore s;
@@ -100,6 +101,16 @@ public class TestTransactionStore extends TestBase {
             task.get();
             store.close();
             s = MVStore.open(fileName);
+            // roll back a bit, until we have some undo log entries
+            assertTrue(s.hasMap("undoLog"));
+            for (int back = 0; back < 100; back++) {
+                int minus = r.nextInt(10);
+                s.rollbackTo(Math.max(0, s.getCurrentVersion() - minus));
+                MVMap<?, ?> undo = s.openMap("undoLog");
+                if (undo.size() > 0) {
+                    break;
+                }
+            }
             ts = new TransactionStore(s);
             List<Transaction> list = ts.getOpenTransactions();
             if (list.size() != 0) {
@@ -111,10 +122,6 @@ public class TestTransactionStore extends TestBase {
             s.close();
             FileUtils.delete(fileName);
             assertFalse(FileUtils.exists(fileName));
-            FileUtils.delete(fileName);
-            assertFalse(FileUtils.exists(fileName));
-            s.close();
-            FileUtils.delete(fileName);
         }
     }