New experimental server-less multi-connection mode

h2/src/main/org/h2/command/Parser.java

@@ -4085,6 +4085,10 @@ public class Parser {
             readIfEqualOrTo();
             read();
             return new NoOperation(session);
+        } else if (readIf("OPEN_NEW")) {
+            readIfEqualOrTo();
+            read();
+            return new NoOperation(session);
         } else if (readIf("RECOVER")) {
             readIfEqualOrTo();
             read();

h2/src/main/org/h2/command/Prepared.java

@@ -368,6 +368,12 @@ public abstract class Prepared {
         return sqlStatement;
     }
 
+    /**
+     * Get the SQL snippet of the value list.
+     *
+     * @param values the value list
+     * @return the SQL snippet
+     */
     protected String getSQL(Value[] values) {
         StringBuffer buff = new StringBuffer();
         for (int i = 0; i < values.length; i++) {
@@ -382,6 +388,12 @@ public abstract class Prepared {
         return buff.toString();
     }
 
+    /**
+     * Get the SQL snippet of the expression list.
+     *
+     * @param list the expression list
+     * @return the SQL snippet
+     */
     protected String getSQL(Expression[] list) {
         StringBuffer buff = new StringBuffer();
         for (int i = 0; i < list.length; i++) {
@@ -396,7 +408,14 @@ public abstract class Prepared {
         return buff.toString();
     }
 
-
+    /**
+     * Set the SQL statement of the exception to the given row.
+     *
+     * @param ex the exception
+     * @param rowId the row number
+     * @param values the values of the row
+     * @return the exception
+     */
     protected SQLException setRow(SQLException ex, int rowId, String values) {
         if (ex instanceof JdbcSQLException) {
             JdbcSQLException e = (JdbcSQLException) ex;

h2/src/main/org/h2/command/dml/TransactionCommand.java

@@ -9,13 +9,11 @@ package org.h2.command.dml;
 import java.sql.SQLException;
 
 import org.h2.command.Prepared;
-import org.h2.constant.SysProperties;
 import org.h2.engine.Database;
 import org.h2.engine.Session;
 import org.h2.log.LogSystem;
 import org.h2.message.Message;
 import org.h2.result.LocalResult;
-import org.h2.store.PageStore;
 
 /**
  * Represents a transactional statement.
@@ -124,12 +122,7 @@ public class TransactionCommand extends Prepared {
             break;
         case CHECKPOINT:
             session.getUser().checkAdmin();
-            if (SysProperties.PAGE_STORE) {
-                PageStore store = session.getDatabase().getPageStore();
-                store.checkpoint();
-            }
-            session.getDatabase().getLog().checkpoint();
-            session.getDatabase().getTempFileDeleter().deleteUnused();
+            session.getDatabase().checkpoint();
             break;
         case SAVEPOINT:
             session.addSavepoint(savepointName);

h2/src/main/org/h2/constant/SysProperties.java

@@ -446,6 +446,15 @@ public class SysProperties {
      */
     public static final boolean RECOMPILE_ALWAYS = getBooleanSetting("h2.recompileAlways", false);
 
+    /**
+     * System property <code>h2.reconnectCheckDelay</code> (default: 250).<br />
+     * Check the .lock.db file every this many milliseconds to detect that the
+     * database was changed. The process writing to the database must first
+     * notify a change in the .lock.db file, then wait twice this many
+     * milliseconds before updating the database.
+     */
+    public static final int RECONNECT_CHECK_DELAY = getIntSetting("h2.reconnectCheckDelay", 250);
+
     /**
      * System property <code>h2.redoBufferSize</code> (default: 262144).<br />
      * Size of the redo buffer (used at startup when recovering).
@@ -558,6 +567,11 @@ public class SysProperties {
      */
     public static final int COLLATOR_CACHE_SIZE = getCollatorCacheSize();
 
+    /**
+     * The current time this class was loaded (in milliseconds).
+     */
+    public static final long TIME_START = System.currentTimeMillis();
+
     private static final String H2_BASE_DIR = "h2.baseDir";
 
     private SysProperties() {

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

@@ -277,6 +277,18 @@ public class ConnectionInfo implements Cloneable {
         userPasswordHash = sha.getKeyPasswordHash(user, password);
     }
 
+    /**
+     * Get a boolean property if it is set and return the value.
+     *
+     * @param key the property name
+     * @param defaultValue the default value
+     * @return the value
+     */
+    public boolean getProperty(String key, boolean defaultValue) {
+        String x = getProperty(key, null);
+        return x == null ? defaultValue : Boolean.valueOf(x).booleanValue();
+    }
+
     /**
      * Remove a boolean property if it is set and return the value.
      *

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

@@ -13,6 +13,7 @@ import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
+import java.util.Properties;
 import java.util.Set;
 import java.util.StringTokenizer;
 
@@ -165,6 +166,10 @@ public class Database implements DataHandler {
     private TempFileDeleter tempFileDeleter = TempFileDeleter.getInstance();
     private PageStore pageStore;
 
+    private Properties reconnectLastLock;
+    private long reconnectCheckNext;
+    private boolean reconnectChangePending;
+
     public Database(String name, ConnectionInfo ci, String cipher) throws SQLException {
         this.compareMode = new CompareMode(null, null, 0);
         this.persistent = ci.isPersistent();
@@ -172,15 +177,18 @@ public class Database implements DataHandler {
         this.databaseName = name;
         this.databaseShortName = parseDatabaseShortName();
         this.cipher = cipher;
-        String lockMethodName = ci.removeProperty("FILE_LOCK", null);
-        this.accessModeLog = ci.removeProperty("ACCESS_MODE_LOG", "rw").toLowerCase();
-        this.accessModeData = ci.removeProperty("ACCESS_MODE_DATA", "rw").toLowerCase();
-        this.autoServerMode = ci.removeProperty("AUTO_SERVER", false);
+        String lockMethodName = ci.getProperty("FILE_LOCK", null);
+        this.accessModeLog = ci.getProperty("ACCESS_MODE_LOG", "rw").toLowerCase();
+        this.accessModeData = ci.getProperty("ACCESS_MODE_DATA", "rw").toLowerCase();
+        this.autoServerMode = ci.getProperty("AUTO_SERVER", false);
         if ("r".equals(accessModeData)) {
             readOnly = true;
             accessModeLog = "r";
         }
         this.fileLockMethod = FileLock.getFileLockMethod(lockMethodName);
+        if (fileLockMethod == FileLock.LOCK_SERIALIZED) {
+            writeDelay = SysProperties.MIN_WRITE_DELAY;
+        }
         this.databaseURL = ci.getURL();
         this.eventListener = ci.getDatabaseEventListenerObject();
         ci.removeDatabaseEventListenerObject();
@@ -199,12 +207,16 @@ public class Database implements DataHandler {
         if (ignoreSummary != null) {
             this.recovery = true;
         }
-        this.multiVersion = ci.removeProperty("MVCC", false);
-        boolean closeAtVmShutdown = ci.removeProperty("DB_CLOSE_ON_EXIT", true);
+        this.multiVersion = ci.getProperty("MVCC", false);
+        boolean closeAtVmShutdown = ci.getProperty("DB_CLOSE_ON_EXIT", true);
         int traceLevelFile = ci.getIntProperty(SetTypes.TRACE_LEVEL_FILE, TraceSystem.DEFAULT_TRACE_LEVEL_FILE);
         int traceLevelSystemOut = ci.getIntProperty(SetTypes.TRACE_LEVEL_SYSTEM_OUT,
                 TraceSystem.DEFAULT_TRACE_LEVEL_SYSTEM_OUT);
         this.cacheType = StringUtils.toUpperEnglish(ci.removeProperty("CACHE_TYPE", CacheLRU.TYPE_NAME));
+        openDatabase(traceLevelFile, traceLevelSystemOut, closeAtVmShutdown);
+    }
+
+    private void openDatabase(int traceLevelFile, int traceLevelSystemOut, boolean closeAtVmShutdown) throws SQLException {
         try {
             open(traceLevelFile, traceLevelSystemOut);
             if (closeAtVmShutdown) {
@@ -295,6 +307,25 @@ public class Database implements DataHandler {
         return modificationDataId;
     }
 
+    private void reconnectModified(boolean pending) {
+        if (readOnly || pending == reconnectChangePending || lock == null) {
+            return;
+        }
+        try {
+            if (pending) {
+                getTrace().debug("wait before writing");
+                Thread.sleep((int) (SysProperties.RECONNECT_CHECK_DELAY * 1.1));
+            }
+            lock.setProperty("modificationDataId", Long.toString(modificationDataId));
+            lock.setProperty("modificationMetaId", Long.toString(modificationMetaId));
+            lock.setProperty("changePending", pending ? "true" : null);
+            lock.save();
+            reconnectChangePending = pending;
+        } catch (Exception e) {
+            getTrace().error("pending:"+ pending, e);
+        }
+    }
+
     public long getNextModificationDataId() {
         return ++modificationDataId;
     }
@@ -478,12 +509,14 @@ public class Database implements DataHandler {
                 }
             }
             if (!readOnly && fileLockMethod != FileLock.LOCK_NO) {
-                lock = new FileLock(traceSystem, Constants.LOCK_SLEEP);
-                lock.lock(databaseName + Constants.SUFFIX_LOCK_FILE, fileLockMethod == FileLock.LOCK_SOCKET);
+                lock = new FileLock(traceSystem, databaseName + Constants.SUFFIX_LOCK_FILE, Constants.LOCK_SLEEP);
+                lock.lock(fileLockMethod);
                 if (autoServerMode) {
                     startServer(lock.getUniqueId());
                 }
             }
+            // wait until pending changes are written
+            isReconnectNeeded();
             if (SysProperties.PAGE_STORE) {
                 PageStore store = getPageStore();
                 if (!store.isNew()) {
@@ -602,7 +635,8 @@ public class Database implements DataHandler {
                 "-key", key, databaseName});
         server.start();
         String address = NetUtils.getLocalAddress() + ":" + server.getPort();
-        lock.addProperty("server", address);
+        lock.setProperty("server", address);
+        lock.save();
     }
 
     private void stopServer() {
@@ -2138,4 +2172,83 @@ public class Database implements DataHandler {
         return null;
     }
 
+    public boolean isReconnectNeeded() {
+        if (fileLockMethod != FileLock.LOCK_SERIALIZED) {
+            return false;
+        }
+        long now = System.currentTimeMillis();
+        if (now < reconnectCheckNext) {
+            return false;
+        }
+        reconnectCheckNext = now + SysProperties.RECONNECT_CHECK_DELAY;
+        if (lock == null) {
+            lock = new FileLock(traceSystem, databaseName + Constants.SUFFIX_LOCK_FILE, Constants.LOCK_SLEEP);
+        }
+        Properties prop;
+        try {
+            while (true) {
+                prop = lock.load();
+                if (prop.equals(reconnectLastLock)) {
+                    return false;
+                }
+                if (prop.getProperty("changePending", null) == null) {
+                    break;
+                }
+                getTrace().debug("delay (change pending)");
+                Thread.sleep(SysProperties.RECONNECT_CHECK_DELAY);
+            }
+            reconnectLastLock = prop;
+        } catch (Exception e) {
+            getTrace().error("readOnly:" + readOnly, e);
+            // ignore
+        }
+        return true;
+    }
+
+    /**
+     * This method is called after writing to the database.
+     */
+    public void afterWriting() throws SQLException {
+        if (fileLockMethod != FileLock.LOCK_SERIALIZED || readOnly) {
+            return;
+        }
+        reconnectCheckNext = System.currentTimeMillis() + 1;
+    }
+
+    /**
+     * Flush all changes when using the serialized mode, and if there are
+     * pending changes.
+     */
+    public void checkpointIfRequired() throws SQLException {
+        if (fileLockMethod != FileLock.LOCK_SERIALIZED || readOnly || !reconnectChangePending) {
+            return;
+        }
+        long now = System.currentTimeMillis();
+        if (now > reconnectCheckNext) {
+            getTrace().debug("checkpoint");
+            checkpoint();
+            reconnectModified(false);
+        }
+    }
+
+    /**
+     * Flush all changes and open a new log file.
+     */
+    public void checkpoint() throws SQLException {
+        if (SysProperties.PAGE_STORE) {
+            pageStore.checkpoint();
+        }
+        getLog().checkpoint();
+        getTempFileDeleter().deleteUnused();
+    }
+
+    /**
+     * This method is called before writing to the log file.
+     */
+    public void beforeWriting() {
+        if (fileLockMethod == FileLock.LOCK_SERIALIZED) {
+            reconnectModified(true);
+        }
+    }
+
 }

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

@@ -16,6 +16,7 @@ import org.h2.constant.ErrorCode;
 import org.h2.constant.SysProperties;
 import org.h2.message.Message;
 import org.h2.message.Trace;
+import org.h2.store.FileLock;
 import org.h2.util.RandomUtils;
 import org.h2.util.StringUtils;
 
@@ -41,7 +42,7 @@ public class Engine {
     private Session openSession(ConnectionInfo ci, boolean ifExists, String cipher) throws SQLException {
         String name = ci.getName();
         Database database;
-        boolean openNew = ci.removeProperty("OPEN_NEW", false);
+        boolean openNew = ci.getProperty("OPEN_NEW", false);
         if (openNew || ci.isUnnamedInMemory()) {
             database = null;
         } else {
@@ -105,8 +106,20 @@ public class Engine {
      */
     public Session getSession(ConnectionInfo ci) throws SQLException {
         try {
+            ConnectionInfo backup = null;
+            String lockMethodName = ci.getProperty("FILE_LOCK", null);
+            int fileLockMethod = FileLock.getFileLockMethod(lockMethodName);
+            if (fileLockMethod == FileLock.LOCK_SERIALIZED) {
+                try {
+                    backup = (ConnectionInfo) ci.clone();
+                } catch (CloneNotSupportedException e) {
+                }
+            }
             Session session = openSession(ci);
             validateUserAndPassword(true);
+            if (backup != null) {
+                session.setConnectionInfo(backup);
+            }
             return session;
         } catch (SQLException e) {
             if (e.getErrorCode() == ErrorCode.WRONG_USER_OR_PASSWORD) {

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

@@ -46,7 +46,7 @@ import org.h2.value.ValueNull;
  * mode, this object resides on the server side and communicates with a
  * SessionRemote object on the client side.
  */
-public class Session implements SessionInterface {
+public class Session extends SessionWithState {
 
     /**
      * The prefix of generated identifiers. It may not have letters, because
@@ -56,9 +56,10 @@ public class Session implements SessionInterface {
     private static int nextSerialId;
 
     private final int serialId = nextSerialId++;
+    private Database database;
+    private ConnectionInfo connectionInfo;
     private User user;
     private int id;
-    private Database database;
     private ObjectArray locks = new ObjectArray();
     private UndoLog undoLog;
     private boolean autoCommit = true;
@@ -97,6 +98,7 @@ public class Session implements SessionInterface {
     private boolean commitOrRollbackDisabled;
     private Table waitForLock;
     private int modificationId;
+    private int modificationIdState;
 
     Session(Database database, User user, int id) {
         this.database = database;
@@ -625,12 +627,13 @@ public class Session implements SessionInterface {
         }
     }
 
-    private void unlockAll() {
+    private void unlockAll() throws SQLException {
         if (SysProperties.CHECK) {
             if (undoLog.size() > 0) {
                 Message.throwInternalError();
             }
         }
+        database.afterWriting();
         if (locks.size() > 0) {
             synchronized (database) {
                 for (int i = 0; i < locks.size(); i++) {
@@ -641,6 +644,10 @@ public class Session implements SessionInterface {
             }
         }
         savepoints = null;
+
+        if (modificationIdState != modificationId) {
+            sessionStateChanged = true;
+        }
     }
 
     private void cleanTempTables(boolean closeSession) throws SQLException {
@@ -1104,4 +1111,20 @@ public class Session implements SessionInterface {
         return modificationId;
     }
 
+    public boolean isReconnectNeeded() {
+        return database.isReconnectNeeded();
+    }
+
+    public SessionInterface reconnect() throws SQLException {
+        readSessionState();
+        Session newSession = Engine.getInstance().getSession(connectionInfo);
+        newSession.sessionState = sessionState;
+        newSession.recreateSessionState();
+        return newSession;
+    }
+
+    public void setConnectionInfo(ConnectionInfo ci) {
+        connectionInfo = ci;
+    }
+
 }

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

@@ -72,4 +72,18 @@ public interface SessionInterface {
      * Cancel the current or next command (called when closing a connection).
      */
     void cancel();
+
+    /**
+     * Check if the database changed and therefore reconnecting is required.
+     *
+     * @return true if reconnecting is required
+     */
+    boolean isReconnectNeeded();
+
+    /**
+     * Close the connection and open a new connection.
+     *
+     * @return the new connection
+     */
+    SessionInterface reconnect() throws SQLException;
 }

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

@@ -41,7 +41,7 @@ import org.h2.value.ValueString;
  * The client side part of a session when using the server mode. This object
  * communicates with a Session on the server side.
  */
-public class SessionRemote implements SessionInterface, SessionFactory, DataHandler {
+public class SessionRemote extends SessionWithState implements SessionFactory, DataHandler {
 
     public static final int SESSION_PREPARE = 0;
     public static final int SESSION_CLOSE = 1;
@@ -81,9 +81,6 @@ public class SessionRemote implements SessionInterface, SessionFactory, DataHand
     private boolean autoReconnect;
     private int lastReconnect;
     private SessionInterface embedded;
-    private boolean sessionStateChanged;
-    private ObjectArray sessionState;
-    private boolean sessionStateUpdating;
     private DatabaseEventListener eventListener;
 
     public SessionRemote() {
@@ -259,7 +256,7 @@ public class SessionRemote implements SessionInterface, SessionFactory, DataHand
                         // OPEN_NEW must be removed now, otherwise
                         // opening a session with AUTO_SERVER fails
                         // if another connection is already open
-                        backup.removeProperty("OPEN_NEW", false);
+                        backup.removeProperty("OPEN_NEW", null);
                         connectServer(backup);
                         return this;
                     }
@@ -451,19 +448,7 @@ public class SessionRemote implements SessionInterface, SessionFactory, DataHand
             // unfortunately
             connectEmbeddedOrServer(true);
         }
-        if (sessionState != null && sessionState.size() > 0) {
-            sessionStateUpdating = true;
-            try {
-                for (int i = 0; i < sessionState.size(); i++) {
-                    String sql = (String) sessionState.get(i);
-                    CommandInterface ci = prepareCommand(sql, Integer.MAX_VALUE);
-                    ci.executeUpdate();
-                }
-            } finally {
-                sessionStateUpdating = false;
-                sessionStateChanged = false;
-            }
-        }
+        recreateSessionState();
         if (eventListener != null) {
             eventListener.setProgress(DatabaseEventListener.STATE_RECONNECTED, databaseName, count,
                     SysProperties.MAX_RECONNECT);
@@ -663,25 +648,16 @@ public class SessionRemote implements SessionInterface, SessionFactory, DataHand
         return lastReconnect;
     }
 
-    /**
-     * Read the session state if necessary.
-     */
-    public void readSessionState() throws SQLException {
-        if (!sessionStateChanged || sessionStateUpdating) {
-            return;
-        }
-        sessionStateChanged = false;
-        sessionState = new ObjectArray();
-        CommandInterface ci = prepareCommand("SELECT * FROM INFORMATION_SCHEMA.SESSION_STATE", Integer.MAX_VALUE);
-        ResultInterface result = ci.executeQuery(0, false);
-        while (result.next()) {
-            Value[] row = result.currentRow();
-            sessionState.add(row[1].getString());
-        }
-    }
-
     public TempFileDeleter getTempFileDeleter() {
         return TempFileDeleter.getInstance();
     }
 
+    public boolean isReconnectNeeded() {
+        return false;
+    }
+
+    public SessionInterface reconnect() {
+        return this;
+    }
+
 }

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

+/*
+ * Copyright 2004-2009 H2 Group. Multiple-Licensed under the H2 License,
+ * Version 1.0, and under the Eclipse Public License, Version 1.0
+ * (http://h2database.com/html/license.html).
+ * Initial Developer: H2 Group
+ */
+package org.h2.engine;
+
+import java.sql.SQLException;
+import org.h2.command.CommandInterface;
+import org.h2.result.ResultInterface;
+import org.h2.util.ObjectArray;
+import org.h2.value.Value;
+
+/**
+ * The base class for both remote and embedded sessions.
+ */
+public abstract class SessionWithState implements SessionInterface {
+
+    protected ObjectArray sessionState;
+    protected boolean sessionStateChanged;
+    private boolean sessionStateUpdating;
+
+    /**
+     * Re-create the session state using the stored sessionState list.
+     */
+    protected void recreateSessionState() throws SQLException {
+        if (sessionState != null && sessionState.size() > 0) {
+            sessionStateUpdating = true;
+            try {
+                for (int i = 0; i < sessionState.size(); i++) {
+                    String sql = (String) sessionState.get(i);
+                    CommandInterface ci = prepareCommand(sql, Integer.MAX_VALUE);
+                    ci.executeUpdate();
+                }
+            } finally {
+                sessionStateUpdating = false;
+                sessionStateChanged = false;
+            }
+        }
+    }
+
+    /**
+     * Read the session state if necessary.
+     */
+    public void readSessionState() throws SQLException {
+        if (!sessionStateChanged || sessionStateUpdating) {
+            return;
+        }
+        sessionStateChanged = false;
+        sessionState = new ObjectArray();
+        CommandInterface ci = prepareCommand("SELECT * FROM INFORMATION_SCHEMA.SESSION_STATE", Integer.MAX_VALUE);
+        ResultInterface result = ci.executeQuery(0, false);
+        while (result.next()) {
+            Value[] row = result.currentRow();
+            sessionState.add(row[1].getString());
+        }
+    }
+
+}

h2/src/main/org/h2/jdbc/JdbcConnection.java

@@ -62,9 +62,6 @@ import java.sql.SQLClientInfoException;
  * </p>
  */
 public class JdbcConnection extends TraceObject implements Connection {
-    // TODO test: check if enough synchronization on jdbc objects
-    // TODO feature: auto-reconnect on lost connection
-
     private String url;
     private String user;
 
@@ -1266,6 +1263,12 @@ public class JdbcConnection extends TraceObject implements Connection {
         if (session.isClosed()) {
             throw Message.getSQLException(ErrorCode.DATABASE_CALLED_AT_SHUTDOWN);
         }
+        if (session.isReconnectNeeded()) {
+            trace.debug("reconnect");
+            session = session.reconnect();
+            trace = session.getTrace();
+            setTrace(trace, TraceObject.CONNECTION, getTraceId());
+        }
     }
 
     String getURL() throws SQLException {

h2/src/main/org/h2/log/LogSystem.java

@@ -509,6 +509,7 @@ public class LogSystem {
                 return;
             }
             database.checkWritingAllowed();
+            database.beforeWriting();
             if (!file.isDataFile()) {
                 storageId = -storageId;
             }
@@ -535,6 +536,7 @@ public class LogSystem {
                 return;
             }
             database.checkWritingAllowed();
+            database.beforeWriting();
             int storageId = record.getStorageId();
             if (!file.isDataFile()) {
                 storageId = -storageId;

h2/src/main/org/h2/message/TraceSystem.java

@@ -178,6 +178,10 @@ public class TraceSystem implements TraceWriter {
         updateLevel();
     }
 
+    public int getLevelSystemOut() {
+        return levelSystemOut;
+    }
+
     /**
      * Set the file trace level.
      *
@@ -209,6 +213,10 @@ public class TraceSystem implements TraceWriter {
         updateLevel();
     }
 
+    public int getLevelFile() {
+        return levelFile;
+    }
+
     private String format(String module, String s) {
         synchronized (dateFormat) {
             return dateFormat.format(new Date()) + module + ": " + s;

h2/src/main/org/h2/res/help.csv

@@ -1843,7 +1843,7 @@ ARRAY
 "Functions (Aggregate)","AVG","
 AVG([DISTINCT] {int | long | decimal | double}): value
 ","
-The average (mean) value. 
+The average (mean) value.
 If no rows are selected, the result is NULL.
 Aggregates are only allowed in select statements.
 ","
@@ -1893,7 +1893,7 @@ GROUP_CONCAT(NAME ORDER BY ID SEPARATOR ', ')
 "Functions (Aggregate)","MAX","
 MAX(value): value
 ","
-The highest value. 
+The highest value.
 If no rows are selected, the result is NULL.
 Aggregates are only allowed in select statements.
 ","
@@ -1903,7 +1903,7 @@ MAX(NAME)
 "Functions (Aggregate)","MIN","
 MIN(value): value
 ","
-The lowest value. 
+The lowest value.
 If no rows are selected, the result is NULL.
 Aggregates are only allowed in select statements.
 ","
@@ -1913,7 +1913,7 @@ MIN(NAME)
 "Functions (Aggregate)","SUM","
 SUM([DISTINCT] {int | long | decimal | double}): value
 ","
-The sum of all values. 
+The sum of all values.
 If no rows are selected, the result is NULL.
 Aggregates are only allowed in select statements.
 ","

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

@@ -54,8 +54,14 @@ public class FileLock {
      */
     public static final int LOCK_SOCKET = 2;
 
+    /**
+     * This locking method means multiple writers are allowed, and they
+     * synchronize themselves.
+     */
+    public static final int LOCK_SERIALIZED = 3;
+
     private static final String MAGIC = "FileLock";
-    private static final String FILE = "file", SOCKET = "socket";
+    private static final String FILE = "file", SOCKET = "socket", SERIALIZED = "serialized";
     private static final int RANDOM_BYTES = 16;
     private static final int SLEEP_GAP = 25;
     private static final int TIME_GRANULARITY = 2000;
@@ -101,30 +107,34 @@ public class FileLock {
      * @param traceSystem the trace system to use
      * @param sleep the number of milliseconds to sleep
      */
-    public FileLock(TraceSystem traceSystem, int sleep) {
+    public FileLock(TraceSystem traceSystem, String fileName, int sleep) {
         this.trace = traceSystem.getTrace(Trace.FILE_LOCK);
+        this.fileName = fileName;
         this.sleep = sleep;
     }
 
     /**
      * Lock the file if possible. A file may only be locked once.
      *
-     * @param fileName the name of the properties file to use
-     * @param allowSocket if the socket locking protocol should be used if
-     *            possible
+     * @param fileLockMethod the file locking method to use
      * @throws SQLException if locking was not successful
      */
-    public synchronized void lock(String fileName, boolean allowSocket) throws SQLException {
+    public synchronized void lock(int fileLockMethod) throws SQLException {
         this.fs = FileSystem.getInstance(fileName);
-        this.fileName = fileName;
         checkServer();
         if (locked) {
             Message.throwInternalError("already locked");
         }
-        if (allowSocket) {
-            lockSocket();
-        } else {
+        switch (fileLockMethod) {
+        case LOCK_FILE:
             lockFile();
+            break;
+        case LOCK_SOCKET:
+            lockSocket();
+            break;
+        case LOCK_SERIALIZED:
+            lockSerialized();
+            break;
         }
         locked = true;
     }
@@ -155,14 +165,18 @@ public class FileLock {
     }
 
     /**
-     * Add a setting to the properties file.
+     * Add or change a setting to the properties. This call does not save the
+     * file.
      *
      * @param key the key
      * @param value the value
      */
-    public void addProperty(String key, String value) throws SQLException {
-        properties.put(key, value);
-        save();
+    public void setProperty(String key, String value) throws SQLException {
+        if (value == null) {
+            properties.remove(key);
+        } else {
+            properties.put(key, value);
+        }
     }
 
     /**
@@ -187,11 +201,10 @@ public class FileLock {
     /**
      * Save the lock file.
      */
-    void save() throws SQLException {
+    public void save() throws SQLException {
         try {
             OutputStream out = fs.openFileOutputStream(fileName, false);
             try {
-                properties.setProperty("method", String.valueOf(method));
                 properties.store(out, MAGIC);
             } finally {
                 out.close();
@@ -242,7 +255,12 @@ public class FileLock {
         }
     }
 
-    private Properties load() throws SQLException {
+    /**
+     * Load the properties file.
+     *
+     * @return the properties
+     */
+    public Properties load() throws SQLException {
         try {
             Properties p2 = SortedProperties.loadProperties(fileName);
             if (trace.isDebugEnabled()) {
@@ -281,9 +299,17 @@ public class FileLock {
         properties.setProperty("id", uniqueId);
     }
 
+    private void lockSerialized() throws SQLException {
+        method = SERIALIZED;
+        properties = new SortedProperties();
+        properties.setProperty("method", String.valueOf(method));
+        setUniqueId();
+    }
+
     private void lockFile() throws SQLException {
         method = FILE;
         properties = new SortedProperties();
+        properties.setProperty("method", String.valueOf(method));
         setUniqueId();
         if (!fs.createNewFile(fileName)) {
             waitUntilOld();
@@ -337,6 +363,7 @@ public class FileLock {
     private void lockSocket() throws SQLException {
         method = SOCKET;
         properties = new SortedProperties();
+        properties.setProperty("method", String.valueOf(method));
         setUniqueId();
         // if this returns 127.0.0.1,
         // the computer is probably not networked
@@ -458,6 +485,8 @@ public class FileLock {
             return FileLock.LOCK_NO;
         } else if (method.equalsIgnoreCase("SOCKET")) {
             return FileLock.LOCK_SOCKET;
+        } else if (method.equalsIgnoreCase("SERIALIZED")) {
+            return FileLock.LOCK_SERIALIZED;
         } else {
             throw Message.getSQLException(ErrorCode.UNSUPPORTED_LOCK_METHOD_1, method);
         }

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

@@ -63,6 +63,7 @@ public class PageStore implements CacheWriter {
     // synchronized correctly (on the index?)
     // TODO two phase commit: append (not patch) commit & rollback
     // TODO remove trace or use isDebugEnabled
+    // TODO recover tool: don't re-do uncommitted operations
 
     /**
      * The smallest possible page size.

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

@@ -142,6 +142,17 @@ public class WriterThread extends Thread {
             if (Constants.FLUSH_INDEX_DELAY != 0) {
                 flushIndexes(database);
             }
+
+            // checkpoint if required
+            try {
+                database.checkpointIfRequired();
+            } catch (SQLException e) {
+                TraceSystem traceSystem = database.getTraceSystem();
+                if (traceSystem != null) {
+                    traceSystem.getTrace(Trace.LOG).error("reconnectCheckpoint", e);
+                }
+            }
+
             LogSystem log = database.getLog();
             if (log == null) {
                 break;
@@ -154,6 +165,7 @@ public class WriterThread extends Thread {
                     traceSystem.getTrace(Trace.LOG).error("flush", e);
                 }
             }
+
             // TODO log writer: could also flush the dirty cache when there is
             // low activity
             int wait = writeDelay;

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

@@ -283,23 +283,15 @@ java org.h2.test.TestAll timer
 
 /*
 
-maybe close the database when a final static field is set to null?
+select 1 from dual a where 1 in(select 1 from dual b
+where 1 in(select 1 from dual c where a.x=1));
 
-use 127.0.0.1 if other addresses don't work
-
-isShutdown
+error message on insert / merge: include SQL statement (at least table name)
 
-PageStore.switchLogIfPossible()
-
-drop table test;
-create table test(id int);
-select 1 from test where 'a'=1;
-Fails: Oracle, PostgreSQL, H2
-Works: MySQL, HSQLDB
+use 127.0.0.1 if other addresses don't work
 
 select for update in mvcc mode: only lock the selected records?
 
-test case for daylight saving time enabled/move to a timezone (locking,...)
 JCR: for each node type, create a table; one 'dynamic' table with parameter;
     option to cache the results
 <link rel="icon" type="image/png" href="/path/image.png">

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

@@ -375,8 +375,8 @@ public abstract class TestBase {
         e.printStackTrace();
         try {
             TraceSystem ts = new TraceSystem(null, false);
-            FileLock lock = new FileLock(ts, 1000);
-            lock.lock("error.lock", false);
+            FileLock lock = new FileLock(ts, "error.lock", 1000);
+            lock.lock(FileLock.LOCK_FILE);
             FileWriter fw = new FileWriter("ERROR.txt", true);
             PrintWriter pw = new PrintWriter(fw);
             e.printStackTrace(pw);

h2/src/test/org/h2/test/unit/TestFileLock.java

@@ -62,9 +62,9 @@ public class TestFileLock extends TestBase implements Runnable {
 
     public void run() {
         while (!stop) {
-            FileLock lock = new FileLock(new TraceSystem(null, false), 100);
+            FileLock lock = new FileLock(new TraceSystem(null, false), FILE, 100);
             try {
-                lock.lock(FILE, allowSockets);
+                lock.lock(allowSockets ? FileLock.LOCK_SOCKET : FileLock.LOCK_FILE);
                 base.trace(lock + " locked");
                 locks++;
                 if (locks > 1) {

h2/src/test/org/h2/test/unit/TestFileLockSerialized.java

+/*
+ * Copyright 2004-2009 H2 Group. Multiple-Licensed under the H2 License,
+ * Version 1.0, and under the Eclipse Public License, Version 1.0
+ * (http://h2database.com/html/license.html).
+ * Initial Developer: H2 Group
+ */
+package org.h2.test.unit;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import org.h2.test.TestBase;
+
+/**
+ * Test the serialized (server-less) mode.
+ */
+public class TestFileLockSerialized extends TestBase {
+
+    /**
+     * Run just this test.
+     *
+     * @param a ignored
+     */
+    public static void main(String[] a) throws Exception {
+        TestBase.createCaller().init().test();
+    }
+
+    public void test() throws Exception {
+
+        // TODO support long running queries
+
+        deleteDb("fileLockSerialized");
+
+        String url = "jdbc:h2:" + baseDir + "/fileLockSerialized";
+        String writeUrl = url + ";FILE_LOCK=SERIALIZED;OPEN_NEW=TRUE";
+        // ;TRACE_LEVEL_SYSTEM_OUT=3
+        // String readUrl = writeUrl + ";ACCESS_MODE_LOG=R;ACCESS_MODE_DATA=R";
+
+        trace("create database");
+        Class.forName("org.h2.Driver");
+        Connection conn = DriverManager.getConnection(writeUrl, "sa", "sa");
+        Statement stat = conn.createStatement();
+        stat.execute("create table test(id int primary key)");
+
+        Connection conn3 = DriverManager.getConnection(writeUrl, "sa", "sa");
+        Statement stat3 = conn3.createStatement();
+
+        Connection conn2 = DriverManager.getConnection(writeUrl, "sa", "sa");
+        Statement stat2 = conn2.createStatement();
+        printResult(stat2, "select * from test");
+
+        stat2.execute("create local temporary table temp(name varchar)");
+        printResult(stat2, "select * from temp");
+
+        trace("insert row 1");
+        stat.execute("insert into test values(1)");
+        trace("insert row 2");
+        stat3.execute("insert into test values(2)");
+        printResult(stat2, "select * from test");
+        printResult(stat2, "select * from temp");
+
+        conn.close();
+        conn2.close();
+        conn3.close();
+    }
+
+    private void printResult(Statement stat, String sql) throws SQLException {
+        trace("query: " + sql);
+        ResultSet rs = stat.executeQuery(sql);
+        int rowCount = 0;
+        while (rs.next()) {
+            trace("  " + rs.getString(1));
+            rowCount++;
+        }
+        trace("  " + rowCount + " row(s)");
+    }
+}