Simplify synchronization (should also be a bit faster).

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

@@ -1159,13 +1159,11 @@ public class Database implements DataHandler {
         }
     }
 
-    private void closeFiles() {
+    private synchronized void closeFiles() {
         try {
-            synchronized (this) {
-                if (pageStore != null) {
-                    pageStore.close();
-                    pageStore = null;
-                }
+            if (pageStore != null) {
+                pageStore.close();
+                pageStore = null;
             }
         } catch (DbException e) {
             trace.error(e, "close");
@@ -1654,13 +1652,11 @@ public class Database implements DataHandler {
      * @param session the session
      * @param transaction the name of the transaction
      */
-    void prepareCommit(Session session, String transaction) {
+    synchronized void prepareCommit(Session session, String transaction) {
         if (readOnly) {
             return;
         }
-        synchronized (this) {
-            pageStore.prepareCommit(session, transaction);
-        }
+        pageStore.prepareCommit(session, transaction);
     }
 
     /**
@@ -1668,28 +1664,24 @@ public class Database implements DataHandler {
      *
      * @param session the session
      */
-    void commit(Session session) {
+    synchronized void commit(Session session) {
         if (readOnly) {
             return;
         }
-        synchronized (this) {
-            if (pageStore != null) {
-                pageStore.commit(session);
-            }
-            session.setAllCommitted();
+        if (pageStore != null) {
+            pageStore.commit(session);
         }
+        session.setAllCommitted();
     }
 
     /**
      * Flush all pending changes to the transaction log.
      */
-    public void flush() {
-        synchronized (this) {
-            if (readOnly || pageStore == null) {
-                return;
-            }
-            pageStore.flushLog();
+    public synchronized void flush() {
+        if (readOnly || pageStore == null) {
+            return;
         }
+        pageStore.flushLog();
     }
 
     public void setEventListener(DatabaseEventListener eventListener) {
@@ -1760,13 +1752,11 @@ public class Database implements DataHandler {
      * Synchronize the files with the file system. This method is called when
      * executing the SQL statement CHECKPOINT SYNC.
      */
-    public void sync() {
-        synchronized (this) {
-            if (readOnly || pageStore == null) {
-                return;
-            }
-            pageStore.sync();
+    public synchronized void sync() {
+        if (readOnly || pageStore == null) {
+            return;
         }
+        pageStore.sync();
     }
 
     public int getMaxMemoryRows() {

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

@@ -412,11 +412,9 @@ public class SessionRemote extends SessionWithState implements DataHandler {
         switchOffCluster();
     }
 
-    public CommandInterface prepareCommand(String sql, int fetchSize) {
-        synchronized (this) {
-            checkClosed();
-            return new CommandRemote(this, transferList, sql, fetchSize);
-        }
+    public synchronized CommandInterface prepareCommand(String sql, int fetchSize) {
+        checkClosed();
+        return new CommandRemote(this, transferList, sql, fetchSize);
     }
 
     /**

h2/src/main/org/h2/table/Column.java

@@ -168,12 +168,10 @@ public class Column {
      * @param row the row
      * @return the value
      */
-    Value computeValue(Session session, Row row) {
-        synchronized (this) {
-            computeTableFilter.setSession(session);
-            computeTableFilter.set(row);
-            return defaultExpression.getValue(session);
-        }
+    synchronized Value computeValue(Session session, Row row) {
+        computeTableFilter.setSession(session);
+        computeTableFilter.set(row);
+        return defaultExpression.getValue(session);
     }
 
     /**