Fix handling SessionWindow without session columns

#### Fix handling of SessionWindow without session columns ✎

- Corrected logic for detecting and handling SessionWindow operations when no session columns are specified, ensuring proper validation and error reporting
- Updated type annotation checks to correctly identify session windows and prevent unsupported WinFilter usage with them
- Added test case to verify correct behavior when SessionWindow is used without explicit session columns, preventing incorrect fusion of filters with such windows

<a href="https://nda.ya.ru/t/qa0kX64r7DqvtN"><font size="2">Autodescription by Yandex Code Assistant</font></a>
commit_hash:9ee57415718e3b085d3eebf843a30a7e919f5e5e

6 files changed, 122 insertions, 4 deletions

diff --git a/yql/essentials/core/common_opt/yql_co_finalizers.cpp b/yql/essentials/core/common_opt/yql_co_finalizers.cpp
index aff124e1188..09ef928e2a2 100644
--- a/yql/essentials/core/common_opt/yql_co_finalizers.cpp
+++ b/yql/essentials/core/common_opt/yql_co_finalizers.cpp
@@ -424,11 +424,11 @@ TExprNode::TPtr FuseFilterWithCalcOverWindow(const TCoFlatMapBase& node, TExprCo
     auto calcs = ExtractCalcsOverWindow(node.Input().Ptr(), ctx);
     YQL_ENSURE(!calcs.empty(), "Empty CalcOverWindow should be processed earlier");
     TCoCalcOverWindowTuple calc(calcs.back());
-    if (!calc.SessionColumns().Empty()) {
+    if (!calc.SessionSpec().Maybe<TCoVoid>()) {
         // we are not ready for fusing session windows yet
         return node.Ptr();
     }
-    YQL_ENSURE(calc.SessionSpec().Maybe<TCoVoid>());
+    YQL_ENSURE(calc.SessionColumns().Empty());
 
     TExprNode::TPtr calcInput = node.Input().Cast<TCoInputBase>().Input().Ptr();
     const TCoConditionalValueBase body = node.Lambda().Body().Cast<TCoConditionalValueBase>();
diff --git a/yql/essentials/core/type_ann/type_ann_list.cpp b/yql/essentials/core/type_ann/type_ann_list.cpp
index 37b14cd9d6f..d1d0ac03ee7 100644
--- a/yql/essentials/core/type_ann/type_ann_list.cpp
+++ b/yql/essentials/core/type_ann/type_ann_list.cpp
@@ -563,15 +563,16 @@ namespace {
         if (!EnsureTuple(winList, ctx)) {
             return IGraphTransformer::TStatus::Error;
         }
+        const bool isSession = sessionSpec && TCoSessionWindowTraits::Match(sessionSpec.Get());
         for (auto winOn: winList.Children()) {
             if (!TCoWinOnBase::Match(winOn.Get())) {
                 auto errMsg = TStringBuilder() << "Expected WinOnRows/WinOnGroups/WinOnRange";
-                if (!sessionColumns) {
+                if (!isSession) {
                     errMsg << "/WinFilter";
                 }
                 ctx.AddError(TIssue(ctx.GetPosition(winOn->Pos()), errMsg));
                 return IGraphTransformer::TStatus::Error;
-            } else if (sessionColumns && sessionColumns->ChildrenSize() && TCoWinFilter::Match(winOn.Get())) {
+            } else if (isSession && TCoWinFilter::Match(winOn.Get())) {
                 ctx.AddError(TIssue(ctx.GetPosition(winOn->Pos()), "WinFilter is not supported with SessionWindow"));
                 return IGraphTransformer::TStatus::Error;
             }
diff --git a/yql/essentials/tests/sql/minirun/part4/canondata/result.json b/yql/essentials/tests/sql/minirun/part4/canondata/result.json
index 05e92a8724e..ea5a507ba59 100644
--- a/yql/essentials/tests/sql/minirun/part4/canondata/result.json
+++ b/yql/essentials/tests/sql/minirun/part4/canondata/result.json
@@ -1491,6 +1491,20 @@
             "uri": "https://{canondata_backend}/1781765/06cae327ea6c6fc81b5ac8d206f80c5f2f779d8e/resource.tar.gz#test.test_weak_field-weak_member_string_copy-default.txt-Results_/results.txt"
         }
     ],
+    "test.test[window-nofuse_filter_with_session_window_nocols-default.txt-Debug]": [
+        {
+            "checksum": "24b2d69edd036c007918636bd7248c1f",
+            "size": 2053,
+            "uri": "https://{canondata_backend}/1814674/c63be47c63f9f12740fe21b1d8bc050b143151f7/resource.tar.gz#test.test_window-nofuse_filter_with_session_window_nocols-default.txt-Debug_/opt.yql"
+        }
+    ],
+    "test.test[window-nofuse_filter_with_session_window_nocols-default.txt-Results]": [
+        {
+            "checksum": "d48d8ae990ffa6bd4b265c56820624e5",
+            "size": 2985,
+            "uri": "https://{canondata_backend}/1814674/c63be47c63f9f12740fe21b1d8bc050b143151f7/resource.tar.gz#test.test_window-nofuse_filter_with_session_window_nocols-default.txt-Results_/results.txt"
+        }
+    ],
     "test.test[window-range_pg/win_range_int_double--Debug]": [
         {
             "checksum": "4c66a67b8095d5d6499ed0d67dd1bea8",
diff --git a/yql/essentials/tests/sql/sql2yql/canondata/result.json b/yql/essentials/tests/sql/sql2yql/canondata/result.json
index c40d47f19c5..e5f9898ca32 100644
--- a/yql/essentials/tests/sql/sql2yql/canondata/result.json
+++ b/yql/essentials/tests/sql/sql2yql/canondata/result.json
@@ -11633,6 +11633,13 @@
             "uri": "https://{canondata_backend}/1942173/8c5157c555883078451557793ef27b73eb262e7a/resource.tar.gz#test_sql2yql.test_window-nofuse_filter_with_session_window_/sql.yql"
         }
     ],
+    "test_sql2yql.test[window-nofuse_filter_with_session_window_nocols]": [
+        {
+            "checksum": "1d42dd66418571202904f17f7d1813f5",
+            "size": 5643,
+            "uri": "https://{canondata_backend}/1942415/b03cb88bfc10f1e7662c3cf258890791821a1e96/resource.tar.gz#test_sql2yql.test_window-nofuse_filter_with_session_window_nocols_/sql.yql"
+        }
+    ],
     "test_sql2yql.test[window-null_type]": [
         {
             "checksum": "e1ea14ebf16ad22d262fb37141f82707",
@@ -19540,6 +19547,11 @@
             "uri": "file://test_sql_format.test_window-nofuse_filter_with_session_window_/formatted.sql"
         }
     ],
+    "test_sql_format.test[window-nofuse_filter_with_session_window_nocols]": [
+        {
+            "uri": "file://test_sql_format.test_window-nofuse_filter_with_session_window_nocols_/formatted.sql"
+        }
+    ],
     "test_sql_format.test[window-null_type]": [
         {
             "uri": "file://test_sql_format.test_window-null_type_/formatted.sql"
diff --git a/yql/essentials/tests/sql/sql2yql/canondata/test_sql_format.test_window-nofuse_filter_with_session_window_nocols_/formatted.sql b/yql/essentials/tests/sql/sql2yql/canondata/test_sql_format.test_window-nofuse_filter_with_session_window_nocols_/formatted.sql
new file mode 100644
index 00000000000..91f51fb194b
--- /dev/null
+++ b/yql/essentials/tests/sql/sql2yql/canondata/test_sql_format.test_window-nofuse_filter_with_session_window_nocols_/formatted.sql
@@ -0,0 +1,55 @@
+PRAGMA config.flags('OptimizerFlags', 'PushdownFiltersOverWindow');
+
+$src = (
+    SELECT
+        *
+    FROM
+        as_table([
+            <|user: Nothing(String?), ts: Nothing(Int32?), payload: 1|>,
+            <|user: 'u1', ts: Nothing(Int32?), payload: 2|>,
+            <|user: Nothing(String?), ts: Nothing(Int32?), payload: 3|>,
+            <|user: 'u1', ts: Nothing(Int32?), payload: 4|>,
+            <|user: Nothing(String?), ts: 1, payload: 5|>,
+            <|user: 'u1', ts: 2, payload: 6|>,
+            <|user: Nothing(String?), ts: 2, payload: 7|>,
+            <|user: 'u1', ts: 3, payload: 8|>,
+            <|user: Nothing(String?), ts: 3, payload: 9|>,
+            <|user: 'u1', ts: 4, payload: 10|>,
+            <|user: Nothing(String?), ts: 10, payload: 11|>,
+            <|user: 'u1', ts: 11, payload: 12|>,
+            <|user: Nothing(String?), ts: 21, payload: 13|>,
+            <|user: 'u1', ts: 22, payload: 14|>,
+            <|user: Nothing(String?), ts: 31, payload: 15|>,
+            <|user: 'u1', ts: 32, payload: 16|>,
+            <|user: Nothing(String?), ts: 50, payload: 17|>,
+            <|user: 'u1', ts: 51, payload: 18|>,
+        ])
+);
+
+$src = (
+    SELECT
+        user,
+        ts,
+        RowNumber() OVER w AS rn,
+    FROM
+        $src
+    WINDOW
+        w AS (
+            PARTITION BY
+                user,
+                SessionWindow(ts, 10)
+            ORDER BY
+                ts
+        )
+);
+
+SELECT
+    *
+FROM
+    $src
+WHERE
+    rn == 1
+ORDER BY
+    user,
+    ts
+;
diff --git a/yql/essentials/tests/sql/suites/window/nofuse_filter_with_session_window_nocols.yql b/yql/essentials/tests/sql/suites/window/nofuse_filter_with_session_window_nocols.yql
new file mode 100644
index 00000000000..4bbf3432d10
--- /dev/null
+++ b/yql/essentials/tests/sql/suites/window/nofuse_filter_with_session_window_nocols.yql
@@ -0,0 +1,36 @@
+PRAGMA config.flags('OptimizerFlags', 'PushdownFiltersOverWindow');
+
+$src = select * from as_table([
+    <|user:Nothing(String?), ts:Nothing(Int32?), payload:1|>,
+    <|user:"u1"            , ts:Nothing(Int32?), payload:2|>,
+    <|user:Nothing(String?), ts:Nothing(Int32?), payload:3|>,
+    <|user:"u1"            , ts:Nothing(Int32?), payload:4|>,
+    <|user:Nothing(String?), ts:1,               payload:5|>,
+    <|user:"u1",             ts:2,               payload:6|>,
+    <|user:Nothing(String?), ts:2,               payload:7|>,
+    <|user:"u1",             ts:3,               payload:8|>,
+    <|user:Nothing(String?), ts:3,               payload:9|>,
+    <|user:"u1",             ts:4,               payload:10|>,
+    <|user:Nothing(String?), ts:10,              payload:11|>,
+    <|user:"u1",             ts:11,              payload:12|>,
+    <|user:Nothing(String?), ts:21,              payload:13|>,
+    <|user:"u1",             ts:22,              payload:14|>,
+    <|user:Nothing(String?), ts:31,              payload:15|>,
+    <|user:"u1",             ts:32,              payload:16|>,
+    <|user:Nothing(String?), ts:50,              payload:17|>,
+    <|user:"u1",             ts:51,              payload:18|>,
+]);
+
+$src = SELECT
+    user,
+    ts,
+    RowNumber() over w as rn,
+FROM $src
+WINDOW w AS (
+    PARTITION BY user, SessionWindow(ts, 10)
+    ORDER BY ts
+);
+
+select * from $src where rn == 1
+ORDER BY user, ts;
+