Issue 518: java.sql.Connection.commit() freezes after LOB modification with…

Issue 518: java.sql.Connection.commit() freezes after LOB modification with EXCLUSIVE connection    

h2/src/docsrc/html/changelog.html

@@ -24,6 +24,7 @@ Change Log
 </li><li>MVStore: concurrency problems have been fixed.
 </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    
 </li></ul>
 
 <h2>Version 1.3.174 (2013-10-19)</h2>

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

@@ -2502,6 +2502,10 @@ public class Database implements DataHandler {
         return conn;
     }
 
+    public Session getLobSession() {
+        return lobSession;
+    }
+    
     public void setLogMode(int log) {
         if (log < 0 || log > 2) {
             throw DbException.getInvalidValueException("LOG", log);

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

@@ -1231,6 +1231,11 @@ public class Session extends SessionWithState {
      * method returns as soon as the exclusive mode has been disabled.
      */
     public void waitIfExclusiveModeEnabled() {
+        // Even in exclusive mode, we have to let the LOB session proceed, or we will
+        // get deadlocks.
+        if (database.getLobSession() == this) {
+            return;
+        }
         while (true) {
             Session exclusive = database.getExclusiveSession();
             if (exclusive == null || exclusive == this) {

h2/src/test/org/h2/test/db/TestLob.java

@@ -59,6 +59,7 @@ public class TestLob extends TestBase {
 
     @Override
     public void test() throws Exception {
+        testCommitOnExclusiveConnection();
         testReadManyLobs();
         testLobSkip();
         testLobSkipPastEnd();
@@ -1486,4 +1487,19 @@ public class TestLob extends TestBase {
         conn.close();
     }
 
+    private static final String MORE_THAN_128_CHARS = "123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789";
+
+    private void testCommitOnExclusiveConnection() throws Exception {
+        deleteDb("lob");
+        Connection conn = getConnection("lob;EXCLUSIVE=1");
+        Statement statement = conn.createStatement();
+        statement.execute("drop table if exists TEST");
+        statement.execute("create table TEST (COL INTEGER, LOB CLOB)");
+        conn.setAutoCommit(false);
+        statement.execute("insert into TEST (COL, LOB) values (1, '" + MORE_THAN_128_CHARS + "')");
+        statement.execute("update TEST set COL=2");
+        // statement.execute("commit"); // OK
+        conn.commit(); // KO : should not hang
+        conn.close();
+    }
 }