SERVER-52556 Versioned CollectionCatalog. Writes are performed using copy-on-write.

Internal mutexes when reading CollectionCatalog are removed, just one mutex for writes are needed.
Lock-free reads helper AutoGetCollectionForReadLockFree stashes a CollectionCatalog consistent with snapshot on OperationContext

2 files changed, 4 insertions, 5 deletions

diff --git a/src/mongo/db/concurrency/d_concurrency.cpp b/src/mongo/db/concurrency/d_concurrency.cpp
index ea4738e55aa..abbd0c875c2 100644
--- a/src/mongo/db/concurrency/d_concurrency.cpp
+++ b/src/mongo/db/concurrency/d_concurrency.cpp
@@ -273,8 +273,7 @@ Lock::CollectionLock::CollectionLock(OperationContext* opCtx,
 
     // 'nsOrUUID' must be a UUID and dbName.
 
-    auto& collectionCatalog = CollectionCatalog::get(opCtx);
-    auto nss = collectionCatalog.resolveNamespaceStringOrUUID(opCtx, nssOrUUID);
+    auto nss = CollectionCatalog::get(opCtx)->resolveNamespaceStringOrUUID(opCtx, nssOrUUID);
 
     // The UUID cannot move between databases so this one dassert is sufficient.
     dassert(_opCtx->lockState()->isDbLockedForMode(nss.db(),
@@ -297,7 +296,7 @@ Lock::CollectionLock::CollectionLock(OperationContext* opCtx,
         // We looked up UUID without a collection lock so it's possible that the
         // collection name changed now. Look it up again.
         prevResolvedNss = nss;
-        nss = collectionCatalog.resolveNamespaceStringOrUUID(opCtx, nssOrUUID);
+        nss = CollectionCatalog::get(opCtx)->resolveNamespaceStringOrUUID(opCtx, nssOrUUID);
     } while (nss != prevResolvedNss);
 }
 
diff --git a/src/mongo/db/concurrency/lock_manager.cpp b/src/mongo/db/concurrency/lock_manager.cpp
index e81bc2f46ff..25987286caf 100644
--- a/src/mongo/db/concurrency/lock_manager.cpp
+++ b/src/mongo/db/concurrency/lock_manager.cpp
@@ -954,8 +954,8 @@ std::string ResourceId::toString() const {
     }
 
     if (getType() == RESOURCE_DATABASE || getType() == RESOURCE_COLLECTION) {
-        CollectionCatalog& catalog = CollectionCatalog::get(getGlobalServiceContext());
-        boost::optional<std::string> resourceName = catalog.lookupResourceName(*this);
+        auto catalog = CollectionCatalog::get(getGlobalServiceContext());
+        boost::optional<std::string> resourceName = catalog->lookupResourceName(*this);
         if (resourceName) {
             ss << ", " << *resourceName;
         }