Revert "SERVER-29506 Require $changeNotification to be the first stage."

This reverts commit 2431e1356823d898ef8af16997d6f63b65b385a5.

1 files changed, 14 insertions, 13 deletions

diff --git a/src/mongo/db/pipeline/document_source_facet.cpp b/src/mongo/db/pipeline/document_source_facet.cpp
index aba1f5f115c..992f3daac11 100644
--- a/src/mongo/db/pipeline/document_source_facet.cpp
+++ b/src/mongo/db/pipeline/document_source_facet.cpp
@@ -99,6 +99,13 @@ vector<pair<string, vector<BSONObj>>> extractRawPipelines(const BSONElement& ele
                                   << ": "
                                   << subPipeElem,
                     subPipeElem.type() == BSONType::Object);
+            auto stageName = subPipeElem.Obj().firstElementFieldName();
+            uassert(
+                40331,
+                str::stream() << "specified stage is not allowed to be used within a $facet stage: "
+                              << subPipeElem,
+                !str::equals(stageName, "$out") && !str::equals(stageName, "$facet"));
+
             rawPipeline.push_back(subPipeElem.embeddedObject());
         }
 
@@ -237,22 +244,16 @@ void DocumentSourceFacet::doReattachToOperationContext(OperationContext* opCtx)
     }
 }
 
-DocumentSource::StageConstraints DocumentSourceFacet::constraints() const {
-    StageConstraints constraints;
-    constraints.isAllowedInsideFacetStage = false;  // Disallow nested $facets.
-
+bool DocumentSourceFacet::needsPrimaryShard() const {
+    // Currently we don't split $facet to have a merger part and a shards part (see SERVER-24154).
+    // This means that if any stage in any of the $facet pipelines requires the primary shard, then
+    // the entire $facet must happen on the merger, and the merger must be the primary shard.
     for (auto&& facet : _facets) {
-        for (auto&& nestedStage : facet.pipeline->getSources()) {
-            if (nestedStage->constraints().mustRunOnPrimaryShardIfSharded) {
-                // Currently we don't split $facet to have a merger part and a shards part (see
-                // SERVER-24154). This means that if any stage in any of the $facet pipelines
-                // requires the primary shard, then the entire $facet must happen on the merger, and
-                // the merger must be the primary shard.
-                constraints.mustRunOnPrimaryShardIfSharded = true;
-            }
+        if (facet.pipeline->needsPrimaryShardMerger()) {
+            return true;
         }
     }
-    return constraints;
+    return false;
 }
 
 DocumentSource::GetDepsReturn DocumentSourceFacet::getDependencies(DepsTracker* deps) const {