SERVER-44771 Introduce 2nd CatalogCache for filtering only

Only on ShardServer (not ReadOnly) use a second catalog cache for
filtering only in order to allow operations in transactions to safely
consult the CatalogCache.

1 files changed, 27 insertions, 0 deletions

diff --git a/src/mongo/db/s/shard_filtering_metadata_refresh.h b/src/mongo/db/s/shard_filtering_metadata_refresh.h
index f378c60622f..7ca5cf1b992 100644
--- a/src/mongo/db/s/shard_filtering_metadata_refresh.h
+++ b/src/mongo/db/s/shard_filtering_metadata_refresh.h
@@ -35,9 +35,36 @@
 
 namespace mongo {
 
+class CatalogCache;
+class CatalogCacheLoader;
+class ServiceContext;
 class OperationContext;
 
 /**
+ * Returns True when a separate CatalogCache must be used for filtering
+ */
+bool hasAdditionalCatalogCacheForFiltering();
+
+/**
+ * CatalogCacheForFiltering is only used on a shard for obtaining the orphan filtering metadata
+ */
+void setCatalogCacheForFiltering(ServiceContext* serviceContext,
+                                 std::unique_ptr<CatalogCache> catalogCache);
+
+
+/**
+ * CatalogCacheLoaderForFiltering is only used on a shard for obtaining the orphan filtering
+ * metadata
+ */
+void setCatalogCacheLoaderForFiltering(ServiceContext* serviceContext,
+                                       std::unique_ptr<CatalogCacheLoader> loader);
+
+// For routing use `CatalogCacheLoader::get()`
+CatalogCacheLoader& getCatalogCacheLoaderForFiltering(ServiceContext* serviceContext);
+CatalogCacheLoader& getCatalogCacheLoaderForFiltering(OperationContext* opCtx);
+
+
+/**
  * Must be invoked whenever code, which is executing on a shard encounters a StaleConfig exception
  * and should be passed the 'version received' from the exception. If the shard's current version is
  * behind 'shardVersionReceived', causes the shard's filtering metadata to be refreshed from the