don't remove DESC sorting for sys view reads

Author: gridnevvvit

ydb/core/kqp/opt/physical/kqp_opt_phy_sort.cpp

@@ -93,6 +93,13 @@ TExprBase KqpRemoveRedundantSortOverReadTable(TExprBase node, TExprContext& ctx,
     }
 
     if (direction == ESortDirection::Reverse) {
+        // For sys views, we need to set reverse flag even if UseSource returns false
+        // because sys view actors can handle reverse direction
+        bool isSysView = tableDesc.Metadata->Kind == EKikimrTableKind::SysView;
+        if (isSysView) {
+            return node;
+        }
+
         if (!UseSource(kqpCtx, tableDesc) && kqpCtx.IsScanQuery()) {
             return node;
         }
@@ -206,7 +213,10 @@ TExprBase KqpRemoveRedundantSortOverReadTableFSM(
     }
 
     if (isReversed) {
-        if (!UseSource(kqpCtx, tableDesc) && kqpCtx.IsScanQuery()) {
+        // For sys views, we need to set reverse flag even if UseSource returns false
+        // because sys view actors can handle reverse direction
+        bool isSysView = tableDesc.Metadata->Kind == EKikimrTableKind::SysView;
+        if (!UseSource(kqpCtx, tableDesc) && kqpCtx.IsScanQuery() && !isSysView) {
             return node;
         }