Support transaction isolation level of "none".

6 files changed, 56 insertions, 24 deletions

diff --git a/src/main/java/com/amazon/carbonado/IsolationLevel.java b/src/main/java/com/amazon/carbonado/IsolationLevel.java
index 7571205..fc8c747 100644
--- a/src/main/java/com/amazon/carbonado/IsolationLevel.java
+++ b/src/main/java/com/amazon/carbonado/IsolationLevel.java
@@ -48,6 +48,12 @@ package com.amazon.carbonado;
 public enum IsolationLevel {

 

     /**

+     * Indicates that no actual transaction is in progress. If this level is

+     * specified when entering a transaction, it uses auto-commit mode.

+     */

+    NONE,

+

+    /**

      * Indicates that dirty reads, non-repeatable reads and phantom reads can

      * occur. This level allows modifications by one transaction to be read by

      * another transaction before any changes have been committed (a "dirty

diff --git a/src/main/java/com/amazon/carbonado/repo/indexed/ManagedIndex.java b/src/main/java/com/amazon/carbonado/repo/indexed/ManagedIndex.java
index 80ad172..bb17067 100644
--- a/src/main/java/com/amazon/carbonado/repo/indexed/ManagedIndex.java
+++ b/src/main/java/com/amazon/carbonado/repo/indexed/ManagedIndex.java
@@ -296,14 +296,10 @@ class ManagedIndex<S extends Storable> implements IndexEntryAccessor<S> {
     void populateIndex(Repository repo, Storage<S> masterStorage) throws RepositoryException {

         MergeSortBuffer buffer;

         Comparator c;

-        Transaction txn;

-

-        if (repo.getTransactionIsolationLevel() == null) {

-            txn = null;

-        } else {

-            txn = repo.enterTopTransaction(IsolationLevel.READ_COMMITTED);

-        }

 

+        // Enter top transaction with isolation level of none to make sure

+        // preload operation does not run in a long nested transaction.

+        Transaction txn = repo.enterTopTransaction(IsolationLevel.NONE);

         try {

             Cursor<S> cursor = masterStorage.query().fetch();

             if (!cursor.hasNext()) {

@@ -335,10 +331,10 @@ class ManagedIndex<S extends Storable> implements IndexEntryAccessor<S> {
             while (cursor.hasNext()) {

                 buffer.add(makeIndexEntry(cursor.next()));

             }

+

+            // No need to commit transaction because no changes should have been made.

         } finally {

-            if (txn != null) {

-                txn.exit();

-            }

+            txn.exit();

         }

 

         buffer.sort();

diff --git a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCRepository.java b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCRepository.java
index 3a6ec68..f9c6d25 100644
--- a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCRepository.java
+++ b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCRepository.java
@@ -79,7 +79,9 @@ public class JDBCRepository
 

     static IsolationLevel mapIsolationLevelFromJdbc(int jdbcLevel) {

         switch (jdbcLevel) {

-        case Connection.TRANSACTION_READ_UNCOMMITTED: default:

+        case Connection.TRANSACTION_NONE: default:

+            return IsolationLevel.NONE;

+        case Connection.TRANSACTION_READ_UNCOMMITTED:

             return IsolationLevel.READ_UNCOMMITTED;

         case Connection.TRANSACTION_READ_COMMITTED:

             return IsolationLevel.READ_COMMITTED;

@@ -92,7 +94,9 @@ public class JDBCRepository
 

     static int mapIsolationLevelToJdbc(IsolationLevel level) {

         switch (level) {

-        case READ_UNCOMMITTED: default:

+        case NONE: default:

+            return Connection.TRANSACTION_NONE;

+        case READ_UNCOMMITTED:

             return Connection.TRANSACTION_READ_UNCOMMITTED;

         case READ_COMMITTED:

             return Connection.TRANSACTION_READ_COMMITTED;

@@ -513,9 +517,14 @@ public class JDBCRepository
 

             // Get connection outside synchronized section since it may block.

             Connection con = mDataSource.getConnection();

-            con.setAutoCommit(false);

-            if (level != mDefaultIsolationLevel) {

-                con.setTransactionIsolation(mapIsolationLevelToJdbc(level));

+

+            if (level == IsolationLevel.NONE) {

+                con.setAutoCommit(true);

+            } else {

+                con.setAutoCommit(false);

+                if (level != mDefaultIsolationLevel) {

+                    con.setTransactionIsolation(mapIsolationLevelToJdbc(level));

+                }

             }

 

             synchronized (mAllTxnMgrs) {

@@ -609,6 +618,8 @@ public class JDBCRepository
         }

 

         switch (desiredLevel) {

+        case NONE:

+            return IsolationLevel.NONE;

         case READ_UNCOMMITTED:

             return mReadUncommittedLevel;

         case READ_COMMITTED:

diff --git a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCTransaction.java b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCTransaction.java
index d92228d..832745b 100644
--- a/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCTransaction.java
+++ b/src/main/java/com/amazon/carbonado/repo/jdbc/JDBCTransaction.java
@@ -34,10 +34,12 @@ import com.amazon.carbonado.IsolationLevel;
  * @author Brian S O'Neill

  */

 class JDBCTransaction {

+    // Use this magic value to indicate that the isolation level need not be

+    // changed when the transaction ends. This is a little optimization to

+    // avoid a round trip call to the remote database.

+    private static final int LEVEL_NOT_CHANGED = -1;

+

     private final Connection mConnection;

-    // Use TRANSACTION_NONE as a magic value to indicate that the isolation

-    // level need not be changed when the transaction ends. This is a little

-    // optimization to avoid a round trip call to the remote database.

     private final int mOriginalLevel;

     private Savepoint mSavepoint;

 

@@ -46,7 +48,7 @@ class JDBCTransaction {
     JDBCTransaction(Connection con) {

         mConnection = con;

         // Don't change level upon abort.

-        mOriginalLevel = Connection.TRANSACTION_NONE;

+        mOriginalLevel = LEVEL_NOT_CHANGED;

     }

 

     /**

@@ -57,16 +59,19 @@ class JDBCTransaction {
 

         if (level == null) {

             // Don't change level upon abort.

-            mOriginalLevel = Connection.TRANSACTION_NONE;

+            mOriginalLevel = LEVEL_NOT_CHANGED;

         } else {

             int newLevel = JDBCRepository.mapIsolationLevelToJdbc(level);

             int originalLevel = mConnection.getTransactionIsolation();

             if (newLevel == originalLevel) {

                 // Don't change level upon abort.

-                mOriginalLevel = Connection.TRANSACTION_NONE;

+                mOriginalLevel = LEVEL_NOT_CHANGED;

             } else {

-                // Don't change level upon abort.

+                // Do change level upon abort.

                 mOriginalLevel = originalLevel;

+                if (originalLevel == Connection.TRANSACTION_NONE) {

+                    mConnection.setAutoCommit(false);

+                }

                 mConnection.setTransactionIsolation(newLevel);

             }

         }

@@ -105,8 +110,12 @@ class JDBCTransaction {
             return mConnection;

         } else {

             mConnection.rollback(mSavepoint);

-            if (mOriginalLevel != Connection.TRANSACTION_NONE) {

-                mConnection.setTransactionIsolation(mOriginalLevel);

+            if (mOriginalLevel != LEVEL_NOT_CHANGED) {

+                if (mOriginalLevel == Connection.TRANSACTION_NONE) {

+                    mConnection.setAutoCommit(true);

+                } else {

+                    mConnection.setTransactionIsolation(mOriginalLevel);

+                }

             }

             mSavepoint = null;

             return null;

diff --git a/src/main/java/com/amazon/carbonado/repo/sleepycat/BDBTransactionManager.java b/src/main/java/com/amazon/carbonado/repo/sleepycat/BDBTransactionManager.java
index 4c6105f..53ca5e4 100644
--- a/src/main/java/com/amazon/carbonado/repo/sleepycat/BDBTransactionManager.java
+++ b/src/main/java/com/amazon/carbonado/repo/sleepycat/BDBTransactionManager.java
@@ -49,6 +49,9 @@ class BDBTransactionManager<Txn> extends TransactionManager<Txn> {
     }

 

     protected Txn createTxn(Txn parent, IsolationLevel level) throws Exception {

+        if (level == IsolationLevel.NONE) {

+            return null;

+        }

         return repository().txn_begin(parent, level);

     }

 

@@ -56,6 +59,9 @@ class BDBTransactionManager<Txn> extends TransactionManager<Txn> {
     protected Txn createTxn(Txn parent, IsolationLevel level, int timeout, TimeUnit unit)

         throws Exception

     {

+        if (level == IsolationLevel.NONE) {

+            return null;

+        }

         if (timeout == 0) {

             return repository().txn_begin_nowait(parent, level);

         } else {

diff --git a/src/main/java/com/amazon/carbonado/spi/TransactionManager.java b/src/main/java/com/amazon/carbonado/spi/TransactionManager.java
index 144b411..e8cc637 100644
--- a/src/main/java/com/amazon/carbonado/spi/TransactionManager.java
+++ b/src/main/java/com/amazon/carbonado/spi/TransactionManager.java
@@ -304,6 +304,8 @@ public abstract class TransactionManager<Txn> {
      *

      * @param parent optional parent transaction

      * @param level required isolation level

+     * @return new transaction, parent transaction, or possibly null if required

+     * isolation level is none

      */

     protected abstract Txn createTxn(Txn parent, IsolationLevel level) throws Exception;

 

@@ -320,6 +322,8 @@ public abstract class TransactionManager<Txn> {
      * @param level required isolation level

      * @param timeout desired timeout for lock acquisition, never negative

      * @param unit timeout unit, never null

+     * @return new transaction, parent transaction, or possibly null if required

+     * isolation level is none

      */

     protected Txn createTxn(Txn parent, IsolationLevel level,

                             int timeout, TimeUnit unit)