Issue 311: File lock mode serialized: selecting the next value from a sequence…

Issue 311: File lock mode serialized: selecting the next value from a sequence didn't work after a pause, because the database thought this is a read-only operation.

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

@@ -172,6 +172,10 @@ public abstract class Command implements CommandInterface {
         Database database = session.getDatabase();
         Object sync = database.isMultiThreaded() ? (Object) session : (Object) database;
         session.waitIfExclusiveModeEnabled();
+        boolean writing = !isReadOnly();
+        if (writing) {
+            database.beforeWriting();
+        }
         synchronized (sync) {
             session.setCurrentCommand(this);
             try {
@@ -191,6 +195,9 @@ public abstract class Command implements CommandInterface {
                 throw e;
             } finally {
                 stop();
+                if (writing) {
+                    database.afterWriting();
+                }
             }
         }
     }

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

@@ -20,6 +20,8 @@ import org.h2.value.ValueNull;
 class CommandContainer extends Command {
 
     private Prepared prepared;
+    private boolean readOnlyKnown;
+    private boolean readOnly;
 
     CommandContainer(Parser parser, String sql, Prepared prepared) {
         super(parser, sql);
@@ -83,7 +85,11 @@ class CommandContainer extends Command {
     }
 
     public boolean isReadOnly() {
-        return prepared.isReadOnly();
+        if (!readOnlyKnown) {
+            readOnly = prepared.isReadOnly();
+            readOnlyKnown = true;
+        }
+        return readOnly;
     }
 
     public ResultInterface queryMeta() {

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

@@ -112,7 +112,7 @@ public class Explain extends Prepared {
     }
 
     public boolean isReadOnly() {
-        return true;
+        return command.isReadOnly();
     }
 
     public int getType() {

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

@@ -38,6 +38,8 @@ public class TestFileLockSerialized extends TestBase {
     }
 
     public void test() throws Exception {
+        println("testSequence");
+        testSequence();
         println("testAutoIncrement");
         testAutoIncrement();
         println("testSequenceFlush");
@@ -73,6 +75,21 @@ public class TestFileLockSerialized extends TestBase {
         deleteDb("fileLockSerialized");
     }
 
+    private void testSequence() throws Exception {
+        deleteDb("fileLockSerialized");
+        String url = "jdbc:h2:" + getBaseDir() + "/fileLockSerialized" +
+                ";FILE_LOCK=SERIALIZED;OPEN_NEW=TRUE;RECONNECT_CHECK_DELAY=10";
+        ResultSet rs;
+        Connection conn1 = DriverManager.getConnection(url);
+        Statement stat1 = conn1.createStatement();
+        stat1.execute("create sequence seq");
+        // 5 times RECONNECT_CHECK_DELAY
+        Thread.sleep(100);
+        rs = stat1.executeQuery("call seq.nextval");
+        rs.next();
+        conn1.close();
+    }
+
     private void testSequenceFlush() throws Exception {
         deleteDb("fileLockSerialized");
         String url = "jdbc:h2:" + getBaseDir() + "/fileLockSerialized;FILE_LOCK=SERIALIZED;OPEN_NEW=TRUE";