SERVER-47407 Avoid using WriteUnitOfWork in index build collection scan loop

(cherry picked from commit e9379fcee79456d3795b598ccad91a0694007d0e)

3 files changed, 22 insertions, 9 deletions

diff --git a/src/mongo/db/catalog/multi_index_block.cpp b/src/mongo/db/catalog/multi_index_block.cpp
index e6e8c96b01c..e1f2589027e 100644
--- a/src/mongo/db/catalog/multi_index_block.cpp
+++ b/src/mongo/db/catalog/multi_index_block.cpp
@@ -504,21 +504,27 @@ Status MultiIndexBlock::insertAllDocumentsInCollection(OperationContext* opCtx,
 
             failPointHangDuringBuild(&hangBeforeIndexBuildOf, "before", objToIndex.value());
 
-            WriteUnitOfWork wunit(opCtx);
-            Status ret = insert(opCtx, objToIndex.value(), loc);
-            if (_method == IndexBuildMethod::kBackground)
-                exec->saveState();
-            if (!ret.isOK()) {
-                // Fail the index build hard.
-                return ret;
-            }
-            wunit.commit();
             if (_method == IndexBuildMethod::kBackground) {
+                WriteUnitOfWork wunit(opCtx);
+
+                Status ret = insert(opCtx, objToIndex.value(), loc);
+                if (!ret.isOK()) {
+                    return ret;
+                }
+                exec->saveState();
+                wunit.commit();
                 try {
                     exec->restoreState();  // Handles any WCEs internally.
                 } catch (...) {
                     return exceptionToStatus();
                 }
+            } else {
+                // The external sorter is not part of the storage engine and therefore does not need
+                // a WriteUnitOfWork to write keys.
+                Status ret = insert(opCtx, objToIndex.value(), loc);
+                if (!ret.isOK()) {
+                    return ret;
+                }
             }
 
             failPointHangDuringBuild(&hangAfterIndexBuildOf, "after", objToIndex.value());
diff --git a/src/mongo/db/index/skipped_record_tracker.cpp b/src/mongo/db/index/skipped_record_tracker.cpp
index d9442b52540..f7c401c12e5 100644
--- a/src/mongo/db/index/skipped_record_tracker.cpp
+++ b/src/mongo/db/index/skipped_record_tracker.cpp
@@ -55,10 +55,14 @@ void SkippedRecordTracker::record(OperationContext* opCtx, const RecordId& recor
         _skippedRecordsTable =
             opCtx->getServiceContext()->getStorageEngine()->makeTemporaryRecordStore(opCtx);
     }
+    // A WriteUnitOfWork may not already be active if the originating operation was part of an
+    // insert into the external sorter.
+    WriteUnitOfWork wuow(opCtx);
     uassertStatusOK(
         _skippedRecordsTable->rs()
             ->insertRecord(opCtx, toInsert.objdata(), toInsert.objsize(), Timestamp::min())
             .getStatus());
+    wuow.commit();
 }
 
 bool SkippedRecordTracker::areAllRecordsApplied(OperationContext* opCtx) const {
diff --git a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
index dc5122b3f8c..8ecd854e399 100644
--- a/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
+++ b/src/mongo/db/storage/wiredtiger/wiredtiger_record_store.cpp
@@ -1016,6 +1016,7 @@ bool WiredTigerRecordStore::findRecord(OperationContext* opCtx,
 
 void WiredTigerRecordStore::deleteRecord(OperationContext* opCtx, const RecordId& id) {
     dassert(opCtx->lockState()->isWriteLocked());
+    invariant(opCtx->lockState()->inAWriteUnitOfWork() || opCtx->lockState()->isNoop());
 
     // Deletes should never occur on a capped collection because truncation uses
     // WT_SESSION::truncate().
@@ -1424,6 +1425,7 @@ Status WiredTigerRecordStore::_insertRecords(OperationContext* opCtx,
                                              const Timestamp* timestamps,
                                              size_t nRecords) {
     dassert(opCtx->lockState()->isWriteLocked());
+    invariant(opCtx->lockState()->inAWriteUnitOfWork() || opCtx->lockState()->isNoop());
 
     // We are kind of cheating on capped collections since we write all of them at once ....
     // Simplest way out would be to just block vector writes for everything except oplog ?
@@ -1569,6 +1571,7 @@ Status WiredTigerRecordStore::updateRecord(OperationContext* opCtx,
                                            const char* data,
                                            int len) {
     dassert(opCtx->lockState()->isWriteLocked());
+    invariant(opCtx->lockState()->inAWriteUnitOfWork() || opCtx->lockState()->isNoop());
 
     WiredTigerCursor curwrap(_uri, _tableId, true, opCtx);
     curwrap.assertInActiveTxn();