Issue 117: Multi-version concurrency: concurrent MERGE statements now work.

h2/src/docsrc/html/changelog.html

@@ -18,7 +18,7 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>-
+<ul><li>Issue 117: Multi-version concurrency: concurrent MERGE statements now work.
 </li></ul>
 
 <h2>Version 1.2.123 (2009-11-08)</h2>

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

@@ -215,9 +215,9 @@ public abstract class Command implements CommandInterface {
                             }
                             try {
                                 if (sync == database) {
-                                    database.wait(100);
+                                    database.wait(10);
                                 } else {
-                                    Thread.sleep(100);
+                                    Thread.sleep(10);
                                 }
                             } catch (InterruptedException e1) {
                                 // ignore

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

@@ -173,14 +173,21 @@ public class Merge extends Prepared {
         }
         int count = update.update();
         if (count == 0) {
-            table.fireBefore(session);
-            table.validateConvertUpdateSequence(session, row);
-            table.fireBeforeRow(session, null, row);
-            table.lock(session, true, false);
-            table.addRow(session, row);
-            session.log(table, UndoLogRecord.INSERT, row);
-            table.fireAfter(session);
-            table.fireAfterRow(session, null, row);
+            try {
+                table.fireBefore(session);
+                table.validateConvertUpdateSequence(session, row);
+                table.fireBeforeRow(session, null, row);
+                table.lock(session, true, false);
+                table.addRow(session, row);
+                session.log(table, UndoLogRecord.INSERT, row);
+                table.fireAfter(session);
+                table.fireAfterRow(session, null, row);
+            } catch (SQLException e) {
+                if (e.getErrorCode() == ErrorCode.DUPLICATE_KEY_1) {
+                    // concurrent merge or insert
+                    throw Message.getSQLException(ErrorCode.CONCURRENT_UPDATE_1, table.getName());
+                }
+            }
         } else if (count != 1) {
             throw Message.getSQLException(ErrorCode.DUPLICATE_KEY_1, table.getSQL());
         }

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

@@ -297,7 +297,6 @@ java org.h2.test.TestAll timer
 
 /*
 
-mvcc merge problem (testConcurrentMerge)
 http://www.apache.org/dev/contrib-email-tips.html
 google app engine
 documentation: rolling review at history.html

h2/src/test/org/h2/test/mvcc/TestMvccMultiThreaded.java

@@ -9,8 +9,6 @@ package org.h2.test.mvcc;
 import java.sql.Connection;
 import java.sql.ResultSet;
 import java.sql.SQLException;
-import java.util.Random;
-
 import org.h2.test.TestBase;
 
 /**
@@ -28,7 +26,7 @@ public class TestMvccMultiThreaded extends TestBase {
     }
 
     public void test() throws Exception {
-        // testConcurrentMerge();
+         testConcurrentMerge();
         testConcurrentUpdate("");
         // not supported currently
         // testConcurrentUpdate(";MULTI_THREADED=TRUE");
@@ -36,14 +34,14 @@ public class TestMvccMultiThreaded extends TestBase {
 
     private void testConcurrentMerge() throws Exception {
         deleteDb("mvccMultiThreaded");
-        int len = 10;
+        int len = 3;
         final Connection[] connList = new Connection[len];
         for (int i = 0; i < len; i++) {
-            Connection conn = getConnection("mvccMultiThreaded;MVCC=TRUE");
+            Connection conn = getConnection("mvccMultiThreaded;MVCC=TRUE;LOCK_TIMEOUT=1000");
             connList[i] = conn;
         }
         Connection conn = connList[0];
-        conn.createStatement().execute("create table test(id int primary key, value int)");
+        conn.createStatement().execute("create table test(id int primary key, name varchar)");
         final SQLException[] ex = new SQLException[1];
         Thread[] threads = new Thread[len];
         final boolean[] stop = new boolean[1];
@@ -52,11 +50,9 @@ public class TestMvccMultiThreaded extends TestBase {
             c.setAutoCommit(false);
             threads[i] = new Thread() {
                 public void run() {
-                    Random random = new Random();
                     while (!stop[0]) {
                         try {
-                            int k = random.nextInt(100);
-                            c.createStatement().execute("merge into test values(" + k + ", " + k + ")");
+                            c.createStatement().execute("merge into test values(1, 'x')");
                             c.commit();
                         } catch (SQLException e) {
                             ex[0] = e;