From bb725d6de95c1b89142d51fb4ec69cbeb042e0cb Mon Sep 17 00:00:00 2001
From: Matt Sullivan <matt.sullivan@fei.com>
Date: Mon, 10 Oct 2011 15:37:19 +1000
Subject: [PATCH] Fix InMemoryBufferedBrowsableElementStore incorrectly
 discarding events

FetchFromPersistentStoreAndCorrelateWithBuffer would enumerate the persistent data store events multiple times, leading to events discarded and not returned.
---
 .../Ncqrs.EventBus/InMemoryBufferedBrowsableElementStore.cs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Extensions/src/Ncqrs.EventBus/InMemoryBufferedBrowsableElementStore.cs b/Extensions/src/Ncqrs.EventBus/InMemoryBufferedBrowsableElementStore.cs
index 3c3da023..2cfadb30 100644
--- a/Extensions/src/Ncqrs.EventBus/InMemoryBufferedBrowsableElementStore.cs
+++ b/Extensions/src/Ncqrs.EventBus/InMemoryBufferedBrowsableElementStore.cs
@@ -41,7 +41,11 @@ private IEnumerable<IProcessingElement> FetchFromBuffer()
 
         private IEnumerable<IProcessingElement> FetchFromPersistentStoreAndCorrelateWithBuffer(string pipelineName)
         {
-            var fetchedFromPersistentStore = _persistentStore.Fetch(pipelineName, _fetchSize);
+            // We need to copy the fetched items to prevent fetchedFromPersistentStore.Any()
+            // and/or CorrelateWithBufffer consuming events and not returning them.
+            // Rx extensions MemoizeAll would be a good solution, but I'm not sure we want
+            // an extra dependency, ToList is fine as long as _fetchSize is reasonable.
+            var fetchedFromPersistentStore = _persistentStore.Fetch(pipelineName, _fetchSize).ToList();
             if (!fetchedFromPersistentStore.Any() || CorrelateWithBufffer(fetchedFromPersistentStore))
             {
                 _inMemoryMode = true;