[YQL-14955] Fix Yield handling in PreserveStream

ref:64282b2038986a328ad3ea120901f71145cda088

1 files changed, 6 insertions, 0 deletions

diff --git a/ydb/library/yql/minikql/comp_nodes/mkql_queue.cpp b/ydb/library/yql/minikql/comp_nodes/mkql_queue.cpp
index 082dea0b660..d398280c8a8 100644
--- a/ydb/library/yql/minikql/comp_nodes/mkql_queue.cpp
+++ b/ydb/library/yql/minikql/comp_nodes/mkql_queue.cpp
@@ -323,14 +323,17 @@ private:
             case EPreserveState::Done:
                 return NUdf::EFetchStatus::Finish;
             case EPreserveState::Feed:
+            case EPreserveState::Yield:
                 break;
             default:
+                Y_VERIFY(Outpace > 0);
                 Buffer.PopFront();
                 --Outpace;
         }
         for (NUdf::TUnboxedValue item; State != EPreserveState::Emit && Outpace <= OutpaceGoal;) {
             switch (Stream.Fetch(item)) {
             case NUdf::EFetchStatus::Yield:
+                State = EPreserveState::Yield;
                 return NUdf::EFetchStatus::Yield;
             case NUdf::EFetchStatus::Finish:
                 State = EPreserveState::Emit;
@@ -343,6 +346,8 @@ private:
                 ++Outpace;
                 if (Outpace > OutpaceGoal) {
                     State = EPreserveState::GoOn;
+                } else {
+                    State = EPreserveState::Feed;
                 }
             }
         }
@@ -358,6 +363,7 @@ private:
     enum class EPreserveState {
         Feed,
         GoOn,
+        Yield,
         Emit,
         Done
     };