1 files changed, 9 insertions, 9 deletions
diff --git a/src/mongo/db/pipeline/document_source_sequential_document_cache.cpp b/src/mongo/db/pipeline/document_source_sequential_document_cache.cpp
index 535c3f5d2be..33c32f096b3 100644
--- a/src/mongo/db/pipeline/document_source_sequential_document_cache.cpp
+++ b/src/mongo/db/pipeline/document_source_sequential_document_cache.cpp
@@ -41,6 +41,7 @@ DocumentSourceSequentialDocumentCache::DocumentSourceSequentialDocumentCache(
     const boost::intrusive_ptr<ExpressionContext>& expCtx, SequentialDocumentCache* cache)
     : DocumentSource(kStageName, expCtx), _cache(cache) {
     invariant(_cache);
+    invariant(!_cache->isAbandoned());
 
     if (_cache->isServing()) {
         _cache->restartIteration();
@@ -80,10 +81,9 @@ DocumentSource::GetNextResult DocumentSourceSequentialDocumentCache::doGetNext()
 
 Pipeline::SourceContainer::iterator DocumentSourceSequentialDocumentCache::doOptimizeAt(
     Pipeline::SourceContainer::iterator itr, Pipeline::SourceContainer* container) {
-    // The DocumentSourceSequentialDocumentCache relies on all other stages in the pipeline being at
-    // the final positions which they would have occupied if no cache stage was present. This should
-    // be the case when we reach this function. The cache should always be the last stage in the
-    // pipeline pre-optimizing.
+    // The DocumentSourceSequentialDocumentCache should always be the last stage in the pipeline
+    // pre-optimization. By the time optimization reaches this point, all preceding stages are in
+    // the final positions which they would have occupied if no cache stage was present.
     invariant(_hasOptimizedPos || std::next(itr) == container->end());
     invariant((*itr).get() == this);
 
@@ -96,7 +96,7 @@ Pipeline::SourceContainer::iterator DocumentSourceSequentialDocumentCache::doOpt
     _hasOptimizedPos = true;
 
     // If the cache is the only stage in the pipeline, return immediately.
-    if (itr == container->begin() && std::next(itr) == container->end()) {
+    if (itr == container->begin()) {
         return container->end();
     }
 
@@ -153,12 +153,12 @@ Pipeline::SourceContainer::iterator DocumentSourceSequentialDocumentCache::doOpt
     return container->end();
 }
 
-Value DocumentSourceSequentialDocumentCache::serialize(const SerializationOptions& opts) const {
-    if (opts.verbosity) {
+Value DocumentSourceSequentialDocumentCache::serialize(
+    boost::optional<ExplainOptions::Verbosity> explain) const {
+    if (explain) {
         return Value(Document{
             {kStageName,
-             Document{{"maxSizeBytes"_sd,
-                       opts.serializeLiteral(static_cast<long long>(_cache->maxSizeBytes()))},
+             Document{{"maxSizeBytes"_sd, Value(static_cast<long long>(_cache->maxSizeBytes()))},
                       {"status"_sd,
                        _cache->isBuilding()
                            ? "kBuilding"_sd