fix gc bucket index compaction (#299)

* fix compaction of m_Payloads and m_AccessTimes in ZenCacheDiskLayer::CacheBucket
* changelog

2 files changed, 6 insertions, 4 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fd79b0da1..f798ae690 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 - Bugfix: Return error code on exit as set by application
 - Bugfix: Fix crash at startup if dead process handles are detected in ZenServerState
 - Bugfix: Fixed assert/error when running block store GC and a block to GC does not exist
+- Bugfix: GC could mix up locations of cache bucket items causing it to return the wrong item for a specific key
 - Improvement: Log details about file and read operation when it fails inside IoBuffer::Materialize()
 
 ## 0.2.10
diff --git a/src/zenserver/cache/structuredcachestore.cpp b/src/zenserver/cache/structuredcachestore.cpp
index a95ae4ca2..2fd8e8be8 100644
--- a/src/zenserver/cache/structuredcachestore.cpp
+++ b/src/zenserver/cache/structuredcachestore.cpp
@@ -1691,10 +1691,11 @@ ZenCacheDiskLayer::CacheBucket::CollectGarbage(GcContext& GcCtx)
 				Index.reserve(EntryCount);
 				for (auto It : m_Index)
 				{
-					size_t EntryIndex = Payloads.size();
-					Payloads.push_back(m_Payloads[EntryIndex]);
-					AccessTimes.push_back(m_AccessTimes[EntryIndex]);
-					Index.insert({It.first, EntryIndex});
+					size_t OldEntryIndex = It.second;
+					size_t NewEntryIndex = Payloads.size();
+					Payloads.push_back(m_Payloads[OldEntryIndex]);
+					AccessTimes.push_back(m_AccessTimes[OldEntryIndex]);
+					Index.insert({It.first, NewEntryIndex});
 				}
 				m_Index.swap(Index);
 				m_Payloads.swap(Payloads);