SERVER-61993 End interleaved mode when skip if reference object contain empty subobj

2 files changed, 42 insertions, 1 deletions

diff --git a/src/mongo/bson/util/bsoncolumn_test.cpp b/src/mongo/bson/util/bsoncolumn_test.cpp
index 6ab45991fb2..17572486ea0 100644
--- a/src/mongo/bson/util/bsoncolumn_test.cpp
+++ b/src/mongo/bson/util/bsoncolumn_test.cpp
@@ -3577,6 +3577,37 @@ TEST_F(BSONColumnTest, InterleavedIncompatibleAfterDeterminedReference) {
     verifyDecompression(binData, elems);
 }
 
+TEST_F(BSONColumnTest, InterleavedSkipAfterEmptySubObj) {
+    BSONColumnBuilder cb("test"_sd);
+
+    std::vector<BSONElement> elems = {
+        createElementObj(BSON("x" << 1 << "y" << 2 << "z" << BSON("z1" << BSONObjBuilder().obj()))),
+        BSONElement()};
+
+    for (auto elem : elems) {
+        if (!elem.eoo())
+            cb.append(elem);
+        else
+            cb.skip();
+    }
+
+    BufBuilder expected;
+    appendInterleavedStart(expected, elems.front().Obj());
+    appendSimple8bControl(expected, 0b1000, 0b0000);
+    appendSimple8bBlocks64(expected, {kDeltaForBinaryEqualValues}, 1);
+    appendSimple8bControl(expected, 0b1000, 0b0000);
+    appendSimple8bBlocks64(expected, {kDeltaForBinaryEqualValues}, 1);
+    appendEOO(expected);
+
+    appendSimple8bControl(expected, 0b1000, 0b0000);
+    appendSimple8bBlock64(expected, boost::none);
+    appendEOO(expected);
+
+    auto binData = cb.finalize();
+    verifyBinary(binData, expected);
+    verifyDecompression(binData, elems);
+}
+
 TEST_F(BSONColumnTest, ObjectEmpty) {
     BSONColumnBuilder cb("test"_sd);
 
diff --git a/src/mongo/bson/util/bsoncolumnbuilder.cpp b/src/mongo/bson/util/bsoncolumnbuilder.cpp
index 3a77fdbd83c..9156b56a5f4 100644
--- a/src/mongo/bson/util/bsoncolumnbuilder.cpp
+++ b/src/mongo/bson/util/bsoncolumnbuilder.cpp
@@ -360,7 +360,17 @@ BSONColumnBuilder& BSONColumnBuilder::append(BSONElement elem) {
 BSONColumnBuilder& BSONColumnBuilder::skip() {
     if (_mode == Mode::kRegular) {
         _state.skip();
-    } else if (_mode == Mode::kSubObjDeterminingReference) {
+        return *this;
+    }
+
+    // If the reference object contain any empty subobjects we need to end interleaved mode as
+    // skipping in all substreams would not be encoded as skipped root object.
+    if (_hasEmptyObj(_referenceSubObj)) {
+        _flushSubObjMode();
+        return skip();
+    }
+
+    if (_mode == Mode::kSubObjDeterminingReference) {
         _bufferedObjElements.push_back(BSONObj());
     } else {
         for (auto&& state : _subobjStates) {