SERVER-39403 Enable accessing sub-pipeline from public const context

1 files changed, 11 insertions, 0 deletions

diff --git a/src/mongo/db/pipeline/document_source_lookup.h b/src/mongo/db/pipeline/document_source_lookup.h
index aeeba4dfa0a..f53dbcee3ad 100644
--- a/src/mongo/db/pipeline/document_source_lookup.h
+++ b/src/mongo/db/pipeline/document_source_lookup.h
@@ -166,6 +166,17 @@ public:
         return !static_cast<bool>(_localField);
     }
 
+    /**
+     * Returns a non-executable pipeline which can be useful for introspection. In this pipeline,
+     * all view definitions are resolved. This pipeline is present in both the sub-pipeline version
+     * of $lookup and the simpler 'localField/foreignField' version, but because it is not tied to
+     * any document to look up it is missing variable definitions for the former type and the $match
+     * stage which will be added to enforce the join criteria for the latter.
+     */
+    const auto& getResolvedIntrospectionPipeline() const {
+        return *_resolvedIntrospectionPipeline;
+    }
+
     const Variables& getVariables_forTest() {
         return _variables;
     }