SERVER-22726 Store path-level multikey information in the KVCatalog.

1 files changed, 25 insertions, 2 deletions

diff --git a/src/mongo/db/catalog/collection_catalog_entry.h b/src/mongo/db/catalog/collection_catalog_entry.h
index a31843b3cce..dd6a1f506f1 100644
--- a/src/mongo/db/catalog/collection_catalog_entry.h
+++ b/src/mongo/db/catalog/collection_catalog_entry.h
@@ -32,6 +32,7 @@
 
 #include "mongo/base/string_data.h"
 #include "mongo/db/catalog/collection_options.h"
+#include "mongo/db/index/multikey_paths.h"
 #include "mongo/db/namespace_string.h"
 #include "mongo/db/record_id.h"
 
@@ -63,11 +64,33 @@ public:
 
     virtual BSONObj getIndexSpec(OperationContext* txn, StringData idxName) const = 0;
 
-    virtual bool isIndexMultikey(OperationContext* txn, StringData indexName) const = 0;
+    /**
+     * Returns true if the index identified by 'indexName' is multikey, and returns false otherwise.
+     *
+     * If the 'multikeyPaths' pointer is non-null, then it must point to an empty vector. If this
+     * index supports tracking path-level multikey information, then this function sets
+     * 'multikeyPaths' as the path components that cause this index to be multikey.
+     *
+     * In particular, if this function returns false and the index supports tracking path-level
+     * multikey information, then 'multikeyPaths' is initialized as a vector with size equal to the
+     * number of elements in the index key pattern of empty sets.
+     */
+    virtual bool isIndexMultikey(OperationContext* txn,
+                                 StringData indexName,
+                                 MultikeyPaths* multikeyPaths) const = 0;
 
+    /**
+     * Sets the index identified by 'indexName' to be multikey.
+     *
+     * If 'multikeyPaths' is non-empty, then it must be a vector with size equal to the number of
+     * elements in the index key pattern. Additionally, at least one path component of the indexed
+     * fields must cause this index to be multikey.
+     *
+     * This function returns true if the index metadata has changed, and returns false otherwise.
+     */
     virtual bool setIndexIsMultikey(OperationContext* txn,
                                     StringData indexName,
-                                    bool multikey = true) = 0;
+                                    const MultikeyPaths& multikeyPaths) = 0;
 
     virtual RecordId getIndexHead(OperationContext* txn, StringData indexName) const = 0;