SERVER-22793 clear buffered WorkingSetIDs on storage engines without document-level concurrency

This ensures that the set of WorkingSetIDs does not grow without bound
on MMAPv1.

(cherry picked from commit aaa5074a59327cdd2d0a462bb27c98f1c1c3ec6a)

4 files changed, 10 insertions, 15 deletions

diff --git a/src/mongo/db/exec/delete.cpp b/src/mongo/db/exec/delete.cpp
index 9db64a9ea20..d0dad6e0db2 100644
--- a/src/mongo/db/exec/delete.cpp
+++ b/src/mongo/db/exec/delete.cpp
@@ -197,11 +197,7 @@ PlanStage::StageState DeleteStage::work(WorkingSetID* out) {
         // saving/restoring state repeatedly?
 
         try {
-            if (supportsDocLocking()) {
-                // Doc-locking engines require this before saveState() since they don't use
-                // invalidations.
-                WorkingSetCommon::prepareForSnapshotChange(_ws);
-            }
+            WorkingSetCommon::prepareForSnapshotChange(_ws);
             child()->saveState();
         } catch (const WriteConflictException& wce) {
             std::terminate();
diff --git a/src/mongo/db/exec/update.cpp b/src/mongo/db/exec/update.cpp
index 0e768074d80..65af0e1a24d 100644
--- a/src/mongo/db/exec/update.cpp
+++ b/src/mongo/db/exec/update.cpp
@@ -877,11 +877,7 @@ PlanStage::StageState UpdateStage::work(WorkingSetID* out) {
 
             // Save state before making changes
             try {
-                if (supportsDocLocking()) {
-                    // Doc-locking engines require this before saveState() since they don't use
-                    // invalidations.
-                    WorkingSetCommon::prepareForSnapshotChange(_ws);
-                }
+                WorkingSetCommon::prepareForSnapshotChange(_ws);
                 child()->saveState();
             } catch (const WriteConflictException& wce) {
                 std::terminate();
diff --git a/src/mongo/db/exec/working_set_common.cpp b/src/mongo/db/exec/working_set_common.cpp
index db5ed4aa8ba..5a0fbf115f2 100644
--- a/src/mongo/db/exec/working_set_common.cpp
+++ b/src/mongo/db/exec/working_set_common.cpp
@@ -63,7 +63,13 @@ bool WorkingSetCommon::fetchAndInvalidateLoc(OperationContext* txn,
 }
 
 void WorkingSetCommon::prepareForSnapshotChange(WorkingSet* workingSet) {
-    dassert(supportsDocLocking());
+    if (!supportsDocLocking()) {
+        // Non doc-locking storage engines use invalidations, so we don't need to examine the
+        // buffered working set ids. But we do need to clear the set of ids in order to keep our
+        // memory utilization in check.
+        workingSet->getAndClearYieldSensitiveIds();
+        return;
+    }
 
     for (auto id : workingSet->getAndClearYieldSensitiveIds()) {
         if (workingSet->isFree(id)) {
diff --git a/src/mongo/db/query/plan_executor.cpp b/src/mongo/db/query/plan_executor.cpp
index 78f9dad20ce..c477fad2a02 100644
--- a/src/mongo/db/query/plan_executor.cpp
+++ b/src/mongo/db/query/plan_executor.cpp
@@ -254,13 +254,10 @@ OperationContext* PlanExecutor::getOpCtx() const {
 void PlanExecutor::saveState() {
     invariant(_currentState == kUsable || _currentState == kSaved);
 
-    // Doc-locking storage engines drop their transactional context after saving state.
     // The query stages inside this stage tree might buffer record ids (e.g. text, geoNear,
     // mergeSort, sort) which are no longer protected by the storage engine's transactional
     // boundaries.
-    if (supportsDocLocking()) {
-        WorkingSetCommon::prepareForSnapshotChange(_workingSet.get());
-    }
+    WorkingSetCommon::prepareForSnapshotChange(_workingSet.get());
 
     if (!killed()) {
         _root->saveState();