Revert "SERVER-56877 IndexCatalogEntryImpl maintains separate copies of multikey paths for readers and writers"

This reverts commit bc095d5cef314bab9fd583c3908eb1cfecb49dd9.

2 files changed, 8 insertions, 15 deletions

diff --git a/src/mongo/db/catalog/index_catalog_entry_impl.cpp b/src/mongo/db/catalog/index_catalog_entry_impl.cpp
index c20bc831c88..7ba3a22f1e4 100644
--- a/src/mongo/db/catalog/index_catalog_entry_impl.cpp
+++ b/src/mongo/db/catalog/index_catalog_entry_impl.cpp
@@ -78,11 +78,10 @@ IndexCatalogEntryImpl::IndexCatalogEntryImpl(OperationContext* const opCtx,
 
     {
         stdx::lock_guard<Latch> lk(_indexMultikeyPathsMutex);
-        const bool isMultikey = _catalogIsMultikey(opCtx, collection, &_indexMultikeyPathsForWrite);
+        const bool isMultikey = _catalogIsMultikey(opCtx, collection, &_indexMultikeyPathsForRead);
         _isMultikeyForRead.store(isMultikey);
         _isMultikeyForWrite.store(isMultikey);
-        _indexMultikeyPathsForRead = _indexMultikeyPathsForWrite;
-        _indexTracksMultikeyPathsInCatalog = !_indexMultikeyPathsForWrite.empty();
+        _indexTracksMultikeyPathsInCatalog = !_indexMultikeyPathsForRead.empty();
     }
 
     auto nss = DurableCatalog::get(opCtx)->getEntry(_catalogId).nss;
@@ -185,12 +184,12 @@ void IndexCatalogEntryImpl::setMultikey(OperationContext* opCtx,
 
     if (_indexTracksMultikeyPathsInCatalog) {
         stdx::lock_guard<Latch> lk(_indexMultikeyPathsMutex);
-        invariant(multikeyPaths.size() == _indexMultikeyPathsForWrite.size());
+        invariant(multikeyPaths.size() == _indexMultikeyPathsForRead.size());
 
         bool newPathIsMultikey = false;
         for (size_t i = 0; i < multikeyPaths.size(); ++i) {
-            if (!std::includes(_indexMultikeyPathsForWrite[i].begin(),
-                               _indexMultikeyPathsForWrite[i].end(),
+            if (!std::includes(_indexMultikeyPathsForRead[i].begin(),
+                               _indexMultikeyPathsForRead[i].end(),
                                multikeyPaths[i].begin(),
                                multikeyPaths[i].end())) {
                 // If 'multikeyPaths' contains a new path component that causes this index to be
@@ -275,11 +274,10 @@ void IndexCatalogEntryImpl::forceSetMultikey(OperationContext* const opCtx,
     {
         stdx::lock_guard<Latch> lk(_indexMultikeyPathsMutex);
         const bool isMultikeyInCatalog =
-            _catalogIsMultikey(opCtx, coll, &_indexMultikeyPathsForWrite);
+            _catalogIsMultikey(opCtx, coll, &_indexMultikeyPathsForRead);
         _isMultikeyForRead.store(isMultikeyInCatalog);
         _isMultikeyForWrite.store(isMultikeyInCatalog);
-        _indexMultikeyPathsForRead = _indexMultikeyPathsForWrite;
-        _indexTracksMultikeyPathsInCatalog = !_indexMultikeyPathsForWrite.empty();
+        _indexTracksMultikeyPathsInCatalog = !_indexMultikeyPathsForRead.empty();
     }
 
     // Since multikey metadata has changed, invalidate the query cache.
@@ -396,7 +394,6 @@ void IndexCatalogEntryImpl::_catalogSetMultikey(OperationContext* opCtx,
     _isMultikeyForRead.store(true);
     if (_indexTracksMultikeyPathsInCatalog) {
         stdx::lock_guard<Latch> lk(_indexMultikeyPathsMutex);
-        _indexMultikeyPathsForRead = _indexMultikeyPathsForWrite;
         for (size_t i = 0; i < multikeyPaths.size(); ++i) {
             _indexMultikeyPathsForRead[i].insert(multikeyPaths[i].begin(), multikeyPaths[i].end());
         }
@@ -415,8 +412,6 @@ void IndexCatalogEntryImpl::_catalogSetMultikey(OperationContext* opCtx,
         // transaction successfully commits. Only after this point may a writer optimize out
         // flipping multikey.
         _isMultikeyForWrite.store(true);
-        stdx::lock_guard<Latch> lk(_indexMultikeyPathsMutex);
-        _indexMultikeyPathsForWrite = _indexMultikeyPathsForRead;
     });
 }
 
diff --git a/src/mongo/db/catalog/index_catalog_entry_impl.h b/src/mongo/db/catalog/index_catalog_entry_impl.h
index 13bd86209fe..6a6f84ff3aa 100644
--- a/src/mongo/db/catalog/index_catalog_entry_impl.h
+++ b/src/mongo/db/catalog/index_catalog_entry_impl.h
@@ -248,7 +248,7 @@ private:
     // this point, future writers do not need to update the catalog.
     mutable AtomicWord<bool> _isMultikeyForWrite;
 
-    // Controls concurrent access to '_indexMultikeyPathsForRead' and '_indexMultikeyPathsForWrite'.
+    // Controls concurrent access to '_indexMultikeyPathsForRead'.
     // We acquire this mutex rather than the RESOURCE_METADATA lock as a performance optimization
     // so that it is cheaper to detect whether there is actually any path-level multikey
     // information to update or not.
@@ -263,8 +263,6 @@ private:
     // causes the index to be multikey.
     mutable MultikeyPaths
         _indexMultikeyPathsForRead;  // May include paths not committed to catalog.
-    mutable MultikeyPaths
-        _indexMultikeyPathsForWrite;  // Paths in catalog updated by a transaction commit.
 
     // The earliest snapshot that is allowed to read this index.
     boost::optional<Timestamp> _minVisibleSnapshot;