Look Ma, no more locks!

h2/src/main/org/h2/mvstore/tx/TransactionMap.java

@@ -10,9 +10,9 @@ import org.h2.mvstore.DataUtils;
 import org.h2.mvstore.MVMap;
 import org.h2.mvstore.Page;
 import org.h2.mvstore.type.DataType;
-import java.util.BitSet;
 
 import java.util.AbstractMap;
+import java.util.BitSet;
 import java.util.Iterator;
 import java.util.Map;
 
@@ -99,8 +99,6 @@ public class TransactionMap<K, V> {
      */
     public long sizeAsLong() {
         TransactionStore store = transaction.store;
-        store.rwLock.readLock().lock();
-        try {
         MVMap<Long, Object[]> undo = transaction.store.undoLog;
 
         BitSet committingTransactions;
@@ -167,9 +165,6 @@ public class TransactionMap<K, V> {
             transaction.store.store.removeMap(temp);
         }
         return size;
-        } finally {
-            transaction.store.rwLock.readLock().unlock();
-        }
     }
 
     /**
@@ -420,8 +415,6 @@ public class TransactionMap<K, V> {
 
     private VersionedValue getValue(K key, long maxLog) {
         TransactionStore store = transaction.store;
-        store.rwLock.readLock().lock();
-        try {
         BitSet committingTransactions;
         MVMap.RootReference mapRootReference;
         MVMap.RootReference undoLogRootReference;
@@ -436,9 +429,6 @@ public class TransactionMap<K, V> {
         Page mapRootPage = mapRootReference.root;
         VersionedValue data = map.get(mapRootPage, key);
         return getValue(mapRootPage, undoRootPage, key, maxLog, data, store.committingTransactions.get());
-        } finally {
-            store.rwLock.readLock().unlock();
-        }
     }
 
     /**

h2/src/main/org/h2/mvstore/tx/TransactionStore.java

@@ -13,7 +13,6 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.atomic.AtomicReferenceArray;
-import java.util.concurrent.locks.ReentrantReadWriteLock;
 import org.h2.mvstore.DataUtils;
 import org.h2.mvstore.MVMap;
 import org.h2.mvstore.MVStore;
@@ -54,12 +53,6 @@ public class TransactionStore {
      */
     final MVMap<Long, Object[]> undoLog;
 
-    /**
-     * the reader/writer lock for the undo-log. Allows us to process multiple
-     * selects in parallel.
-     */
-    final ReentrantReadWriteLock rwLock = new ReentrantReadWriteLock();
-
     /**
      * The map of maps.
      */
@@ -169,8 +162,6 @@ public class TransactionStore {
                     store.removeMap(temp);
                 }
             }
-            rwLock.writeLock().lock();
-            try {
             if (!undoLog.isEmpty()) {
                 Long key = undoLog.firstKey();
                 while (key != null) {
@@ -200,9 +191,6 @@ public class TransactionStore {
                     }
                 }
             }
-            } finally {
-                rwLock.writeLock().unlock();
-            }
             init = true;
         }
     }
@@ -277,8 +265,6 @@ public class TransactionStore {
         if(!init) {
             init();
         }
-        rwLock.readLock().lock();
-        try {
         ArrayList<Transaction> list = new ArrayList<>();
         int transactionId = 0;
         BitSet bitSet = openTransactions.get();
@@ -291,9 +277,6 @@ public class TransactionStore {
             }
         }
         return list;
-        } finally {
-            rwLock.readLock().unlock();
-        }
     }
 
     /**
@@ -387,8 +370,6 @@ public class TransactionStore {
      */
     long addUndoLogRecord(int transactionId, long logId, Object[] undoLogRecord) {
         Long undoKey = getOperationId(transactionId, logId);
-        rwLock.writeLock().lock();
-        try {
         if (logId == 0) {
             if (undoLog.containsKey(undoKey)) {
                 throw DataUtils.newIllegalStateException(
@@ -399,9 +380,6 @@ public class TransactionStore {
             }
         }
         undoLog.put(undoKey, undoLogRecord);
-        } finally {
-            rwLock.writeLock().unlock();
-        }
         return undoKey;
     }
 
@@ -413,8 +391,6 @@ public class TransactionStore {
      */
     public void removeUndoLogRecord(int transactionId, long logId) {
         Long undoKey = getOperationId(transactionId, logId);
-        rwLock.writeLock().lock();
-        try {
         Object[] old = undoLog.remove(undoKey);
         if (old == null) {
             throw DataUtils.newIllegalStateException(
@@ -422,9 +398,6 @@ public class TransactionStore {
                     "Transaction {0} was concurrently rolled back",
                     transactionId);
         }
-        } finally {
-            rwLock.writeLock().unlock();
-        }
     }
 
     /**
@@ -455,8 +428,6 @@ public class TransactionStore {
         flipCommittingTransactionsBit(transactionId, true);
 
         CommitDecisionMaker commitDecisionMaker = new CommitDecisionMaker();
-        // TODO could synchronize on blocks (100 at a time or so)
-        rwLock.writeLock().lock();
         try {
             for (long logId = 0; logId < maxLogId; logId++) {
                 Long undoKey = getOperationId(transactionId, logId);
@@ -481,7 +452,6 @@ public class TransactionStore {
                 undoLog.remove(undoKey);
             }
         } finally {
-            rwLock.writeLock().unlock();
             flipCommittingTransactionsBit(transactionId, false);
         }
     }
@@ -635,9 +605,6 @@ public class TransactionStore {
      * @param toLogId the log id to roll back to
      */
     void rollbackTo(Transaction t, long maxLogId, long toLogId) {
-        // TODO could synchronize on blocks (100 at a time or so)
-        rwLock.writeLock().lock();
-        try {
         int transactionId = t.getId();
         RollbackDecisionMaker decisionMaker = new RollbackDecisionMaker(this, transactionId, toLogId, t.listener);
         for (long logId = maxLogId - 1; logId >= toLogId; logId--) {
@@ -645,9 +612,6 @@ public class TransactionStore {
             undoLog.operate(undoKey, null, decisionMaker);
             decisionMaker.reset();
         }
-        } finally {
-            rwLock.writeLock().unlock();
-        }
     }
 
     /**
@@ -667,8 +631,6 @@ public class TransactionStore {
             private Change current;
 
             private void fetchNext() {
-                rwLock.writeLock().lock();
-                try {
                 int transactionId = t.getId();
                 while (logId >= toLogId) {
                     Long undoKey = getOperationId(transactionId, logId);
@@ -692,9 +654,6 @@ public class TransactionStore {
                         return;
                     }
                 }
-                } finally {
-                    rwLock.writeLock().unlock();
-                }
                 current = null;
             }