SERVER-38360 Prevent $out writing to ns read from in the same pipeline

This restriction only applies to $out with modes "insertDocuments" and
"replaceDocuments".

1 files changed, 10 insertions, 1 deletions

diff --git a/src/mongo/db/pipeline/document_source_graph_lookup.cpp b/src/mongo/db/pipeline/document_source_graph_lookup.cpp
index ee745dedda6..eea8b370cdf 100644
--- a/src/mongo/db/pipeline/document_source_graph_lookup.cpp
+++ b/src/mongo/db/pipeline/document_source_graph_lookup.cpp
@@ -476,7 +476,7 @@ DocumentSourceGraphLookUp::DocumentSourceGraphLookUp(
     // We append an additional BSONObj to '_fromPipeline' as a placeholder for the $match stage
     // we'll eventually construct from the input document.
     _fromPipeline.reserve(_fromPipeline.size() + 1);
-    _fromPipeline.push_back(BSONObj());
+    _fromPipeline.push_back(BSON("$match" << BSONObj()));
 }
 
 intrusive_ptr<DocumentSourceGraphLookUp> DocumentSourceGraphLookUp::create(
@@ -602,4 +602,13 @@ intrusive_ptr<DocumentSource> DocumentSourceGraphLookUp::createFromBson(
 
     return std::move(newSource);
 }
+
+void DocumentSourceGraphLookUp::addInvolvedCollections(
+    stdx::unordered_set<NamespaceString>* collectionNames) const {
+    collectionNames->insert(_fromExpCtx->ns);
+    auto introspectionPipeline = uassertStatusOK(Pipeline::parse(_fromPipeline, _fromExpCtx));
+    for (auto&& stage : introspectionPipeline->getSources()) {
+        stage->addInvolvedCollections(collectionNames);
+    }
+}
 }  // namespace mongo