SERVER-19153 push $match as far forward as possible

1 files changed, 5 insertions, 36 deletions

diff --git a/src/mongo/db/pipeline/document_source_unwind.cpp b/src/mongo/db/pipeline/document_source_unwind.cpp
index a03bd1e8034..02b8dc62355 100644
--- a/src/mongo/db/pipeline/document_source_unwind.cpp
+++ b/src/mongo/db/pipeline/document_source_unwind.cpp
@@ -232,43 +232,12 @@ BSONObjSet DocumentSourceUnwind::getOutputSorts() {
     return out;
 }
 
-Pipeline::SourceContainer::iterator DocumentSourceUnwind::optimizeAt(
-    Pipeline::SourceContainer::iterator itr, Pipeline::SourceContainer* container) {
-    invariant(*itr == this);
-
-    if (auto nextMatch = dynamic_cast<DocumentSourceMatch*>((*std::next(itr)).get())) {
-        std::set<std::string> fields = {_unwindPath.fullPath()};
-
-        if (_indexPath) {
-            fields.insert((*_indexPath).fullPath());
-        }
-
-        auto splitMatch = nextMatch->splitSourceBy(fields);
-
-        invariant(splitMatch.first || splitMatch.second);
-
-        if (!splitMatch.first && splitMatch.second) {
-            // No optimization was possible.
-            return std::next(itr);
-        }
-
-        container->erase(std::next(itr));
-
-        // If splitMatch.second is not null, then there is a new $match stage to insert after
-        // ourselves.
-        if (splitMatch.second) {
-            container->insert(std::next(itr), std::move(splitMatch.second));
-        }
-
-        if (splitMatch.first) {
-            container->insert(itr, std::move(splitMatch.first));
-            if (std::prev(itr) == container->begin()) {
-                return std::prev(itr);
-            }
-            return std::prev(std::prev(itr));
-        }
+DocumentSource::GetModPathsReturn DocumentSourceUnwind::getModifiedPaths() const {
+    std::set<std::string> modifiedFields{_unwindPath.fullPath()};
+    if (_indexPath) {
+        modifiedFields.insert(_indexPath->fullPath());
     }
-    return std::next(itr);
+    return {GetModPathsReturn::Type::kFiniteSet, std::move(modifiedFields)};
 }
 
 Value DocumentSourceUnwind::serialize(bool explain) const {