SERVER-19153 push $match as far forward as possible

1 files changed, 11 insertions, 0 deletions

diff --git a/src/mongo/db/pipeline/parsed_inclusion_projection.h b/src/mongo/db/pipeline/parsed_inclusion_projection.h
index eb2bc1877bc..8cd04514b53 100644
--- a/src/mongo/db/pipeline/parsed_inclusion_projection.h
+++ b/src/mongo/db/pipeline/parsed_inclusion_projection.h
@@ -121,6 +121,11 @@ public:
 
     void injectExpressionContext(const boost::intrusive_ptr<ExpressionContext>& expCtx);
 
+    /**
+     * Recursively add all paths that are preserved by this inclusion projection.
+     */
+    void addPreservedPaths(std::set<std::string>* preservedPaths) const;
+
 private:
     // Helpers for the Document versions above. These will apply the transformation recursively to
     // each element of any arrays, and ensure non-documents are handled appropriately.
@@ -214,6 +219,12 @@ public:
         return DocumentSource::EXHAUSTIVE_FIELDS;
     }
 
+    DocumentSource::GetModPathsReturn getModifiedPaths() const final {
+        std::set<std::string> preservedPaths;
+        _root->addPreservedPaths(&preservedPaths);
+        return {DocumentSource::GetModPathsReturn::Type::kAllExcept, std::move(preservedPaths)};
+    }
+
     /**
      * Apply this exclusion projection to 'inputDoc'.
      *