TransactionStore: new persisted transaction state "committing".

h2/src/main/org/h2/engine/Database.java

@@ -648,7 +648,7 @@ public class Database implements DataHandler {
             rec.execute(this, systemSession, eventListener);
         }
         if (mvStore != null) {
-            mvStore.rollback();
+            mvStore.initTransactions();
         }
         recompileInvalidViews(systemSession);
         starting = false;

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

@@ -51,7 +51,7 @@ TransactionStore:
 - support reading the undo log
 
 MVStore:
-- rolling docs review: at convert "Features" to top-level (linked) entries
+- rolling docs review: at "Features"
 - additional test async write / read algorithm for speed and errors
 - move setters to the builder, except for setRetainVersion, setReuseSpace,
     and settings that are persistent (setStoreVersion)
@@ -61,7 +61,7 @@ MVStore:
 - maybe split database into multiple files, to speed up compact
 - auto-compact from time to time and on close
 - test and possibly improve compact operation (for large dbs)
-- possibly split chunk data into immutable and mutable
+- possibly split chunk metadata into immutable and mutable
 - compact: avoid processing pages using a counting bloom filter
 - defragment (re-creating maps, specially those with small pages)
 - chunk header: store changed chunk data as row; maybe after the root
@@ -69,8 +69,8 @@ MVStore:
 - is there a better name for the file header,
 -- if it's no longer always at the beginning of a file? store header?
 - on insert, if the child page is already full, don't load and modify it
--- split directly (for leaves with 1 entry)
-- maybe let a chunk point to possible next chunks
+-- split directly (specially for leaves with one large entry)
+- maybe let a chunk point to a list of potential next chunks
 -- (so no fixed location header is needed)
 - support stores that span multiple files (chunks stored in other files)
 - triggers (can be implemented with a custom map)
@@ -107,6 +107,7 @@ MVStore:
 - unit test for the FreeSpaceList; maybe find a simpler implementation
 - support opening (existing) maps by id
 - more consistent null handling (keys/values sometimes may be null)
+- logging mechanism, specially for operations in a background thread
 
 */
 
@@ -959,6 +960,7 @@ public class MVStore {
         buff.position(0);
         fileWriteCount++;
         DataUtils.writeFully(file, filePos, buff);
+        
         fileSize = Math.max(fileSize, filePos + buff.position());
         if (buff.capacity() <= 4 * 1024 * 1024) {
             writeBuffer = buff;
@@ -1846,7 +1848,13 @@ public class MVStore {
                         // ignore
                     }
                 }
-                store.storeInBackground();
+                try {
+                    store.storeInBackground();
+                } catch (Exception e) {
+                    int todo;
+                    // TODO throw the exception in the main thread
+                    // at some point, or log the problem
+                }
             }
         }
 

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

@@ -191,12 +191,15 @@ public class MVTableEngine implements TableEngine {
         }
 
         /**
-         * Rollback all open transactions.
+         * Commit all transactions that are in the committing state, and
+         * rollback all open transactions.
          */
-        public void rollback() {
+        public void initTransactions() {
             List<Transaction> list = transactionStore.getOpenTransactions();
             for (Transaction t : list) {
-                if (t.getStatus() != Transaction.STATUS_PREPARED) {
+                if (t.getStatus() == Transaction.STATUS_COMITTING) {
+                    t.commit();
+                } else if (t.getStatus() != Transaction.STATUS_PREPARED) {
                     t.rollback();
                 }
             }

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

@@ -44,6 +44,8 @@ public class TransactionStore {
 
     /**
      * The undo log.
+     * If the first entry for a transaction doesn't have a logId of 0, then
+     * the transaction is committing (partially committed). 
      * Key: [ transactionId, logId ], value: [ opType, mapId, key, oldValue ].
      */
     final MVMap<long[], Object[]> undoLog;
@@ -141,7 +143,12 @@ public class TransactionStore {
                 int status;
                 String name;
                 if (data == null) {
-                    status = Transaction.STATUS_OPEN;
+                    key[1] = 0;
+                    if (undoLog.containsKey(key)) {
+                        status = Transaction.STATUS_OPEN;
+                    } else {
+                        status = Transaction.STATUS_COMITTING;
+                    }
                     name = null;
                 } else {
                     status = (Integer) data[0];
@@ -232,12 +239,18 @@ public class TransactionStore {
             return;
         }
         synchronized (undoLog) {
+            t.setStatus(Transaction.STATUS_COMITTING);
             for (long logId = 0; logId < maxLogId; logId++) {
                 commitIfNeeded();
                 long[] undoKey = new long[] { t.getId(), logId };
                 Object[] op = undoLog.get(undoKey);
                 if (op == null) {
-                    int todoImprove;
+                    // partially committed: load next
+                    undoKey = undoLog.ceilingKey(undoKey);
+                    if (undoKey == null || undoKey[0] != t.getId()) {
+                        break;
+                    }
+                    logId = undoKey[1] - 1;
                     continue;
                 }
                 int opType = (Integer) op[0];
@@ -342,7 +355,12 @@ public class TransactionStore {
                 long[] undoKey = new long[] { t.getId(), logId };
                 Object[] op = undoLog.get(undoKey);
                 if (op == null) {
-                    int todoImprove;
+                    // partially rolled back: load previous
+                    undoKey = undoLog.floorKey(undoKey);
+                    if (undoKey == null || undoKey[0] != t.getId()) {
+                        break;
+                    }
+                    logId = undoKey[1] + 1;
                     continue;
                 }
                 int mapId = ((Integer) op[1]).intValue();
@@ -385,11 +403,16 @@ public class TransactionStore {
             private void fetchNext() {
                 synchronized (undoLog) {
                     while (logId >= toLogId) {
-                        Object[] op = undoLog.get(new long[] {
-                                t.getId(), logId });
+                        long[] undoKey = new long[] { t.getId(), logId };
+                        Object[] op = undoLog.get(undoKey);
                         logId--;
                         if (op == null) {
-                            int todoImprove;
+                            // partially rolled back: load previous
+                            undoKey = undoLog.floorKey(undoKey);
+                            if (undoKey == null || undoKey[0] != t.getId()) {
+                                break;
+                            }
+                            logId = undoKey[1];
                             continue;
                         }
                         int mapId = ((Integer) op[1]).intValue();
@@ -460,20 +483,28 @@ public class TransactionStore {
      */
     public static class Transaction {
 
+        /**
+         * The status of a closed transaction (committed or rolled back).
+         */
+        public static final int STATUS_CLOSED = 0;
+
         /**
          * The status of an open transaction.
          */
-        public static final int STATUS_OPEN = 0;
+        public static final int STATUS_OPEN = 1;
 
         /**
          * The status of a prepared transaction.
          */
-        public static final int STATUS_PREPARED = 1;
+        public static final int STATUS_PREPARED = 2;
 
         /**
-         * The status of a closed transaction (committed or rolled back).
+         * The status of a transaction that is being committed, but possibly not
+         * yet finished. A transactions can go into this state when the store is
+         * closed while the transaction is committing. When opening a store,
+         * such transactions should be committed.
          */
-        public static final int STATUS_CLOSED = 2;
+        public static final int STATUS_COMITTING = 3;
 
         /**
          * The operation type for changes in a map.

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

@@ -15,7 +15,9 @@ import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Random;
+import java.util.concurrent.atomic.AtomicInteger;
 
+import org.h2.mvstore.MVMap;
 import org.h2.mvstore.MVStore;
 import org.h2.mvstore.db.TransactionStore;
 import org.h2.mvstore.db.TransactionStore.Change;
@@ -24,6 +26,7 @@ import org.h2.mvstore.db.TransactionStore.TransactionMap;
 import org.h2.store.fs.FileUtils;
 import org.h2.test.TestBase;
 import org.h2.util.New;
+import org.h2.util.Task;
 
 /**
  * Test concurrent transactions.
@@ -42,6 +45,7 @@ public class TestTransactionStore extends TestBase {
     @Override
     public void test() throws Exception {
         FileUtils.createDirectories(getBaseDir());
+        testStopWhileCommitting();
         testGetModifiedMaps();
         testKeyIterator();
         testMultiStatement();
@@ -51,6 +55,70 @@ public class TestTransactionStore extends TestBase {
         testSingleConnection();
         testCompareWithPostgreSQL();
     }
+    
+    private void testStopWhileCommitting() throws Exception {
+        String fileName = getBaseDir() + "/testStopWhileCommitting.h3";
+        FileUtils.delete(fileName);
+
+        for (int i = 0; i < 10;) {
+            MVStore s;
+            TransactionStore ts;
+            Transaction tx;
+            TransactionMap<Integer, String> m;
+
+            s = MVStore.open(fileName);
+            ts = new TransactionStore(s);
+            tx = ts.begin();
+            s.setReuseSpace(false);
+            m = tx.openMap("test");
+            final String value = "x" + i;
+            for (int j = 0; j < 1000; j++) {
+                m.put(j, value);
+            }
+            final AtomicInteger state = new AtomicInteger();
+            final MVStore store = s;
+            final MVMap<Integer, String> other = s.openMap("other");
+            Task task = new Task() {
+
+                @Override
+                public void call() throws Exception {
+                    for (int i = 0; state.get() < Integer.MAX_VALUE; i++) {
+                        state.set(i);
+                        other.put(i, value);
+                        store.store();
+                    }
+                }
+            };
+            task.execute();
+            // wait for the task to start
+            while (state.get() < 1) {
+                Thread.yield();
+            }
+            // commit while writing in the task
+            tx.commit();
+            // stop writing
+            state.set(Integer.MAX_VALUE);
+            // wait for the task to stop
+            task.get();
+            store.close();
+            s = MVStore.open(fileName);
+            ts = new TransactionStore(s);
+            List<Transaction> list = ts.getOpenTransactions();
+            if (list.size() != 0) {
+                tx = list.get(0);
+                if (tx.getStatus() == Transaction.STATUS_COMITTING) {
+                    i++;
+                }
+            }
+            s.close();
+            FileUtils.delete(fileName);
+            assertFalse(FileUtils.exists(fileName));
+            FileUtils.delete(fileName);
+            assertFalse(FileUtils.exists(fileName));
+            s.close();
+            FileUtils.delete(fileName);        
+        }
+    }
 
     private void testGetModifiedMaps() {
         MVStore s = MVStore.open(null);