SERVER-11831 Use documentFromBsonWithDeps in agg again

This bypasses new query framework projection and replaces it with a much faster
dedicated code path. The downside is that it prevents using covering indexes
in the cases where that was allowed (SERVER-12015).

3 files changed, 15 insertions, 5 deletions

diff --git a/src/mongo/db/pipeline/document_source.h b/src/mongo/db/pipeline/document_source.h
index d0148be0bf5..f3b282182a0 100644
--- a/src/mongo/db/pipeline/document_source.h
+++ b/src/mongo/db/pipeline/document_source.h
@@ -422,6 +422,7 @@ namespace mongo {
         BSONObj _query;
         BSONObj _sort;
         BSONObj _projection;
+        bool _haveDeps;
         ParsedDeps _dependencies;
         intrusive_ptr<DocumentSourceLimit> _limit;
         long long _docsAddedToBatches; // for _limit enforcement
diff --git a/src/mongo/db/pipeline/document_source_cursor.cpp b/src/mongo/db/pipeline/document_source_cursor.cpp
index 324d83e3236..bba5ab951fe 100644
--- a/src/mongo/db/pipeline/document_source_cursor.cpp
+++ b/src/mongo/db/pipeline/document_source_cursor.cpp
@@ -97,9 +97,12 @@ namespace mongo {
         BSONObj obj;
         Runner::RunnerState state;
         while ((state = runner->getNext(&obj, NULL)) == Runner::RUNNER_ADVANCED) {
-            // TODO SERVER-11831: consider using documentFromBsonWithDeps(obj, _dependencies)
-
-            _currentBatch.push_back(Document(obj));
+            if (_haveDeps) {
+                _currentBatch.push_back(documentFromBsonWithDeps(obj, _dependencies));
+            }
+            else {
+                _currentBatch.push_back(Document(obj));
+            }
 
             if (_limit) {
                 if (++_docsAddedToBatches == _limit->getLimit()) {
@@ -178,8 +181,10 @@ namespace {
         if (info->isScanAndOrderSet())
             out[TypeExplain::scanAndOrder()] = Value(info->getScanAndOrder());
 
+#if 0 // Disabled pending SERVER-12015 since until then no aggs will be index only.
         if (info->isIndexOnlySet())
             out[TypeExplain::indexOnly()] = Value(info->getIndexOnly());
+#endif
 
         if (info->isIndexBoundsSet())
             out[TypeExplain::indexBounds()] = Value(info->getIndexBounds());
@@ -250,6 +255,7 @@ namespace {
                                                CursorId cursorId,
                                                const intrusive_ptr<ExpressionContext> &pCtx)
         : DocumentSource(pCtx)
+        , _haveDeps(false)
         , _docsAddedToBatches(0)
         , _ns(ns)
         , _cursorId(cursorId)
@@ -265,5 +271,6 @@ namespace {
     void DocumentSourceCursor::setProjection(const BSONObj& projection, const ParsedDeps& deps) {
         _projection = projection;
         _dependencies = deps;
+        _haveDeps = true;
     }
 }
diff --git a/src/mongo/db/pipeline/pipeline_d.cpp b/src/mongo/db/pipeline/pipeline_d.cpp
index c3a9e1b8e8f..130cd87d01a 100644
--- a/src/mongo/db/pipeline/pipeline_d.cpp
+++ b/src/mongo/db/pipeline/pipeline_d.cpp
@@ -184,10 +184,12 @@ namespace {
         bool sortInRunner = false;
         if (sortStage) {
             CanonicalQuery* cq;
+            // Passing an empty projection since it is faster to use documentFromBsonWithDeps.
+            // This will need to change to support covering indexes (SERVER-12015).
             uassertStatusOK(CanonicalQuery::canonicalize(pExpCtx->ns,
                                                          queryObj,
                                                          sortObj,
-                                                         projection,
+                                                         BSONObj(), // projection
                                                          &cq));
             Runner* rawRunner;
             if (getRunner(cq, &rawRunner, runnerOptions).isOK()) {
@@ -209,7 +211,7 @@ namespace {
             uassertStatusOK(CanonicalQuery::canonicalize(pExpCtx->ns,
                                                          queryObj,
                                                          noSort,
-                                                         projection,
+                                                         BSONObj(), // projection
                                                          &cq));
 
             Runner* rawRunner;