diff --git a/src/graph/optimizer/rule/PushFilterDownScanVerticesRule.cpp b/src/graph/optimizer/rule/PushFilterDownScanVerticesRule.cpp
index 00ed8a00711..6bc600c9440 100644
--- a/src/graph/optimizer/rule/PushFilterDownScanVerticesRule.cpp
+++ b/src/graph/optimizer/rule/PushFilterDownScanVerticesRule.cpp
@@ -43,7 +43,7 @@ StatusOr<OptRule::TransformResult> PushFilterDownScanVerticesRule::transform(
   auto sv = static_cast<const ScanVertices *>(svGroupNode->node());
   auto qctx = ctx->qctx();
   auto pool = qctx->objPool();
-  auto condition = filter->condition()->clone();
+  auto condition = DCHECK_NOTNULL(filter->condition())->clone();
 
   auto visitor = graph::ExtractFilterExprVisitor::makePushGetVertices(pool);
   condition->accept(&visitor);
diff --git a/src/graph/planner/match/ScanSeek.cpp b/src/graph/planner/match/ScanSeek.cpp
index 40ee85dc015..8b08a157858 100644
--- a/src/graph/planner/match/ScanSeek.cpp
+++ b/src/graph/planner/match/ScanSeek.cpp
@@ -92,8 +92,11 @@ StatusOr<SubPlan> ScanSeek::transformNode(NodeContext *nodeCtx) {
       prev = notEmpty;
     }
   }
-  auto *filter = Filter::make(qctx, scanVertices, prev);
-  plan.root = filter;
+  if (prev != nullptr) {
+    // prev equals to nullptr happend when there are no tags in whole space
+    auto *filter = Filter::make(qctx, scanVertices, prev);
+    plan.root = filter;
+  }
 
   nodeCtx->initialExpr = InputPropertyExpression::make(pool, kVid);
   return plan;
diff --git a/src/graph/session/ClientSession.h b/src/graph/session/ClientSession.h
index 2568a07c01d..9001da52fd9 100644
--- a/src/graph/session/ClientSession.h
+++ b/src/graph/session/ClientSession.h
@@ -119,7 +119,7 @@ class ClientSession final {
     }
   }
 
-  const meta::cpp2::Session& getSession() const {
+  meta::cpp2::Session getSession() const {
     folly::RWSpinLock::ReadHolder rHolder(rwSpinLock_);
     return session_;
   }
diff --git a/src/parser/parser.yy b/src/parser/parser.yy
index 013c238d3d4..373f1fd9a25 100644
--- a/src/parser/parser.yy
+++ b/src/parser/parser.yy
@@ -1382,9 +1382,12 @@ vid
         $$ = ConstantExpression::make(qctx->objPool(), *$1);
         delete $1;
     }
+    // This reduce rule aim to report more friendly error message
     | VARIABLE {
         $$ = nullptr;
-        delete($1);
+        SCOPE_EXIT {
+            delete($1);
+        };
         if (qctx->existParameter(*$1)) {
             throw nebula::GraphParser::syntax_error(@1, "Parameter is not supported in vid");
         } else {