From fb3696bc72ce7bcbf17a5188b7fec1c5b690ad23 Mon Sep 17 00:00:00 2001
From: "Brian S. O'Neill" <bronee@gmail.com>
Date: Mon, 2 Oct 2006 06:08:44 +0000
Subject: Add support SNAPSHOT isolation level.

---
 src/main/java/com/amazon/carbonado/IsolationLevel.java | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'src/main/java/com/amazon/carbonado/IsolationLevel.java')

diff --git a/src/main/java/com/amazon/carbonado/IsolationLevel.java b/src/main/java/com/amazon/carbonado/IsolationLevel.java
index 5f963b2..7571205 100644
--- a/src/main/java/com/amazon/carbonado/IsolationLevel.java
+++ b/src/main/java/com/amazon/carbonado/IsolationLevel.java
@@ -26,6 +26,7 @@ package com.amazon.carbonado;
  * <li>{@link #READ_UNCOMMITTED}
  * <li>{@link #READ_COMMITTED}
  * <li>{@link #REPEATABLE_READ}
+ * <li>{@link #SNAPSHOT}
  * <li>{@link #SERIALIZABLE}
  * </ul>
  *
@@ -35,6 +36,11 @@ package com.amazon.carbonado;
  * iteration. It releases locks during iteration rather than holding on to them
  * until the transaction exits.
  *
+ * <p>{@code SNAPSHOT} isolation is special in that it uses multiversion
+ * concurrency control (MVCC). A commit may fail with an {@link
+ * OptimisticLockException}. Few repositories are expected to support this
+ * level, however.
+ *
  * @author Brian S O'Neill
  * @see Repository#enterTransaction(IsolationLevel)
  * @see Transaction
@@ -71,6 +77,13 @@ public enum IsolationLevel {
      */
     REPEATABLE_READ,
 
+    /**
+     * Indicates that dirty reads, non-repeatable reads and phantom reads are
+     * prevented. Commits can still fail however, as snapshot isolation avoids
+     * using locks.
+     */
+    SNAPSHOT,
+
     /**
      * Indicates that dirty reads, non-repeatable reads and phantom reads are
      * prevented. Phantoms are records returned as a result of a search, but
-- 
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