diff --git a/src/graph/visitor/PropertyTrackerVisitor.cpp b/src/graph/visitor/PropertyTrackerVisitor.cpp
index ce3042c717a..0456876ba52 100644
--- a/src/graph/visitor/PropertyTrackerVisitor.cpp
+++ b/src/graph/visitor/PropertyTrackerVisitor.cpp
@@ -279,8 +279,10 @@ void PropertyTrackerVisitor::visit(AttributeExpression *expr) {
 }
 
 void PropertyTrackerVisitor::visit(FunctionCallExpression *expr) {
+  // length function support `STRING` input too, so we can't ignore it directly
+  // TODO add type info to variable to help optimize it.
   static const std::unordered_set<std::string> ignoreFuncs = {
-      "src", "dst", "type", "typeid", "id", "rank", "length"};
+      "src", "dst", "type", "typeid", "id", "rank" /*, "length"*/};
 
   auto funName = expr->name();
   std::transform(funName.begin(), funName.end(), funName.begin(), ::tolower);
diff --git a/tests/tck/features/bugfix/NullInputOfLength.feature b/tests/tck/features/bugfix/NullInputOfLength.feature
new file mode 100644
index 00000000000..3b767ac9603
--- /dev/null
+++ b/tests/tck/features/bugfix/NullInputOfLength.feature
@@ -0,0 +1,18 @@
+# Copyright (c) 2022 vesoft inc. All rights reserved.
+#
+# This source code is licensed under Apache 2.0 License.
+Feature: Null input of length function
+
+  Background:
+    Given a graph with space named "nba"
+
+  Scenario: Null input of length function
+    When executing query:
+      """
+      match p = (v)-[:like]->() where id(v) == 'Tim Duncan'
+      return length(v.player.name) as l, length(p) as lp
+      """
+    Then the result should be, in any order:
+      | l  | lp |
+      | 10 | 1  |
+      | 10 | 1  |
diff --git a/tests/tck/features/optimizer/PrunePropertiesRule.feature b/tests/tck/features/optimizer/PrunePropertiesRule.feature
index b85e1581152..21b69feadd7 100644
--- a/tests/tck/features/optimizer/PrunePropertiesRule.feature
+++ b/tests/tck/features/optimizer/PrunePropertiesRule.feature
@@ -439,14 +439,14 @@ Feature: Prune Properties rule
       | length(p) |
       | 1         |
     And the execution plan should be:
-      | id | name           | dependencies | operator info                                                                                                                 |
-      | 13 | Project        | 11           |                                                                                                                               |
-      | 11 | Limit          | 5            |                                                                                                                               |
-      | 5  | AppendVertices | 4            | {  "props": "[{\"props\":[\"_tag\"],\"tagId\":8}, {\"props\":[\"_tag\"],\"tagId\":9}, {\"props\":[\"_tag\"],\"tagId\":10}]" } |
-      | 4  | Traverse       | 2            | {"vertexProps": "", "edgeProps": "[{\"type\": 3, \"props\": [\"_type\", \"_rank\", \"_dst\"]}]"  }                            |
-      | 2  | Dedup          | 1            |                                                                                                                               |
-      | 1  | PassThrough    | 3            |                                                                                                                               |
-      | 3  | Start          |              |                                                                                                                               |
+      | id | name           | dependencies | operator info                                                                                                                                                                                                                                                                                  |
+      | 13 | Project        | 11           |                                                                                                                                                                                                                                                                                                |
+      | 11 | Limit          | 5            |                                                                                                                                                                                                                                                                                                |
+      | 5  | AppendVertices | 4            | {  "props": "[{\"props\":[\"_tag\", \"name\", \"speciality\"],\"tagId\":8}, {\"props\":[\"_tag\", \"name\", \"age\"],\"tagId\":9}, {\"props\":[\"_tag\", \"name\"],\"tagId\":10}]" }                                                                                                           |
+      | 4  | Traverse       | 2            | {"vertexProps": "[{\"props\":[\"name\", \"age\", \"_tag\"],\"tagId\":9}, {\"props\":[\"name\", \"speciality\", \"_tag\"],\"tagId\":8}, {\"props\":[\"name\", \"_tag\"],\"tagId\":10}]", "edgeProps": "[{\"type\": 3, \"props\": [\"_type\", \"_rank\", \"_dst\", \"_src\", \"likeness\"]}]"  } |
+      | 2  | Dedup          | 1            |                                                                                                                                                                                                                                                                                                |
+      | 1  | PassThrough    | 3            |                                                                                                                                                                                                                                                                                                |
+      | 3  | Start          |              |                                                                                                                                                                                                                                                                                                |
     When profiling query:
       """
       MATCH p = (a:player)-[e:like*1..3]->(b:player{age:39})
@@ -466,20 +466,20 @@ Feature: Prune Properties rule
       | "Tracy McGrady" | 1        |
       | "Tracy McGrady" | 3        |
     And the execution plan should be:
-      | id | name           | dependencies | operator info                                                                                                                                  |
-      | 14 | Project        | 13           |                                                                                                                                                |
-      | 13 | BiInnerJoin    | 15,12        |                                                                                                                                                |
-      | 15 | Project        | 17           |                                                                                                                                                |
-      | 17 | AppendVertices | 16           | {  "props": "[{\"props\":[\"name\",\"age\"],\"tagId\":9}]" }                                                                                   |
-      | 16 | Traverse       | 2            | {"vertexProps": "", "edgeProps": "[{\"type\": 3, \"props\": [\"_type\", \"_rank\", \"_dst\"]}]"  }                                             |
-      | 2  | Dedup          | 1            |                                                                                                                                                |
-      | 1  | PassThrough    | 3            |                                                                                                                                                |
-      | 3  | Start          |              |                                                                                                                                                |
-      | 12 | Project        | 18           |                                                                                                                                                |
-      | 18 | AppendVertices | 10           | {  "props": "[{\"props\":[\"_tag\"],\"tagId\":10}]" }                                                                                          |
-      | 10 | Traverse       | 8            | {"vertexProps": "[{\"props\":[\"name\",\"age\"],\"tagId\":9}]", "edgeProps": "[{\"type\": 4, \"props\": [\"_type\", \"_rank\", \"_dst\"]}]"  } |
-      | 8  | Argument       |              |                                                                                                                                                |
-      | 9  | Start          |              |                                                                                                                                                |
+      | id | name           | dependencies | operator info                                                                                                                                                                                                                                                                                  |
+      | 14 | Project        | 13           |                                                                                                                                                                                                                                                                                                |
+      | 13 | BiInnerJoin    | 15,12        |                                                                                                                                                                                                                                                                                                |
+      | 15 | Project        | 17           |                                                                                                                                                                                                                                                                                                |
+      | 17 | AppendVertices | 16           | {  "props": "[{\"props\":[\"_tag\", \"name\", \"speciality\"],\"tagId\":8}, {\"props\":[\"_tag\", \"name\", \"age\"],\"tagId\":9}, {\"props\":[\"_tag\", \"name\"],\"tagId\":10}]" }                                                                                                           |
+      | 16 | Traverse       | 2            | {"vertexProps": "[{\"props\":[\"name\", \"age\", \"_tag\"],\"tagId\":9}, {\"props\":[\"name\", \"speciality\", \"_tag\"],\"tagId\":8}, {\"props\":[\"name\", \"_tag\"],\"tagId\":10}]", "edgeProps": "[{\"type\": 3, \"props\": [\"_type\", \"_rank\", \"_dst\", \"_src\", \"likeness\"]}]"  } |
+      | 2  | Dedup          | 1            |                                                                                                                                                                                                                                                                                                |
+      | 1  | PassThrough    | 3            |                                                                                                                                                                                                                                                                                                |
+      | 3  | Start          |              |                                                                                                                                                                                                                                                                                                |
+      | 12 | Project        | 18           |                                                                                                                                                                                                                                                                                                |
+      | 18 | AppendVertices | 10           | {  "props": "[{\"props\":[\"_tag\"],\"tagId\":10}]" }                                                                                                                                                                                                                                          |
+      | 10 | Traverse       | 8            | {"vertexProps": "[{\"props\":[\"name\", \"age\", \"_tag\"],\"tagId\":9}, {\"props\":[\"name\", \"speciality\", \"_tag\"],\"tagId\":8}, {\"props\":[\"name\", \"_tag\"],\"tagId\":10}]", "edgeProps": "[{\"type\": 4, \"props\": [\"_type\", \"_rank\", \"_dst\"]}]"  }                         |
+      | 8  | Argument       |              |                                                                                                                                                                                                                                                                                                |
+      | 9  | Start          |              |                                                                                                                                                                                                                                                                                                |
 
   @distonly
   Scenario: union match