YQL-15785 Drop ForwardList only in case of single usage.

2 files changed, 6 insertions, 1 deletions

diff --git a/ydb/library/yql/core/common_opt/yql_co_flow1.cpp b/ydb/library/yql/core/common_opt/yql_co_flow1.cpp
index 00914926b1..ace50f61f9 100644
--- a/ydb/library/yql/core/common_opt/yql_co_flow1.cpp
+++ b/ydb/library/yql/core/common_opt/yql_co_flow1.cpp
@@ -1356,6 +1356,11 @@ TExprNode::TPtr OptimizeToFlow(const TExprNode::TPtr& node, TExprContext& ctx, T
         return node->Head().HeadPtr();
     }
 
+    if (node->Head().IsCallable("ForwardList")) {
+        YQL_CLOG(DEBUG, Core) << "Drop " << node->Head().Content() << " under " << node->Content();
+        return ctx.ChangeChild(*node, 0U,  node->Head().HeadPtr());
+    }
+
     if (node->Head().IsCallable("Chopper")) {
         YQL_CLOG(DEBUG, Core) << "Swap " << node->Head().Content() << " with " << node->Content();
         auto children = node->Head().ChildrenList();
diff --git a/ydb/library/yql/core/common_opt/yql_co_simple1.cpp b/ydb/library/yql/core/common_opt/yql_co_simple1.cpp
index fc5e95e870..f71c96811a 100644
--- a/ydb/library/yql/core/common_opt/yql_co_simple1.cpp
+++ b/ydb/library/yql/core/common_opt/yql_co_simple1.cpp
@@ -2369,7 +2369,7 @@ TExprNode::TPtr OptimizeToFlow(const TExprNode::TPtr& node, TExprContext& ctx) {
         return ctx.NewCallable(node->Pos(), "EmptyIterator", {ExpandType(node->Pos(), *node->GetTypeAnn(), ctx)});
     }
 
-    if (node->Head().IsCallable({"ForwardList", "LazyList", "ToStream"})) {
+    if (node->Head().IsCallable({"LazyList", "ToStream"})) {
         YQL_CLOG(DEBUG, Core) << "Drop " << node->Head().Content() << " under " << node->Content();
         return ctx.ChangeChildren(*node, node->Head().ChildrenList());
     }