SERVER-26461 Don't exclude fields when entire document is needed.

2 files changed, 28 insertions, 1 deletions

diff --git a/src/mongo/db/pipeline/dependencies.cpp b/src/mongo/db/pipeline/dependencies.cpp
index 9a6016ed20a..bb6b7175ae5 100644
--- a/src/mongo/db/pipeline/dependencies.cpp
+++ b/src/mongo/db/pipeline/dependencies.cpp
@@ -42,7 +42,7 @@ using std::vector;
 namespace str = mongoutils::str;
 
 BSONObj DepsTracker::toProjection() const {
-    if (fields.empty()) {
+    if (fields.empty() && !needWholeDocument) {
         if (_needTextScore) {
             // We only need the text score, but there is no easy way to express this in the query
             // projection language. We use $noFieldsNeeded with a textScore meta-projection since
diff --git a/src/mongo/db/pipeline/dependencies_test.cpp b/src/mongo/db/pipeline/dependencies_test.cpp
index 9f2294d46aa..5bfd008bbfe 100644
--- a/src/mongo/db/pipeline/dependencies_test.cpp
+++ b/src/mongo/db/pipeline/dependencies_test.cpp
@@ -131,5 +131,32 @@ TEST(DependenciesToProjectionTest,
         BSON(Document::metaFieldTextScore << metaTextScore << "a" << 1 << "_id" << 0));
 }
 
+TEST(DependenciesToProjectionTest, ShouldProduceEmptyObjectIfThereAreNoDependencies) {
+    DepsTracker deps(DepsTracker::MetadataAvailable::kTextScore);
+    deps.fields = {};
+    deps.needWholeDocument = false;
+    deps.setNeedTextScore(false);
+    ASSERT_BSONOBJ_EQ(deps.toProjection(), BSONObj());
+}
+
+TEST(DependenciesToProjectionTest, ShouldAttemptToExcludeOtherFieldsIfOnlyTextScoreIsNeeded) {
+    DepsTracker deps(DepsTracker::MetadataAvailable::kTextScore);
+    deps.fields = {};
+    deps.needWholeDocument = false;
+    deps.setNeedTextScore(true);
+    ASSERT_BSONOBJ_EQ(deps.toProjection(),
+                      BSON("_id" << 0 << "$noFieldsNeeded" << 1 << Document::metaFieldTextScore
+                                 << metaTextScore));
+}
+
+TEST(DependenciesToProjectionTest,
+     ShouldRequireTextScoreIfNoFieldsPresentButWholeDocumentIsNeeded) {
+    DepsTracker deps(DepsTracker::MetadataAvailable::kTextScore);
+    deps.fields = {};
+    deps.needWholeDocument = true;
+    deps.setNeedTextScore(true);
+    ASSERT_BSONOBJ_EQ(deps.toProjection(), BSON(Document::metaFieldTextScore << metaTextScore));
+}
+
 }  // namespace
 }  // namespace mongo