From e4b8af73866d24302c889c4896deec739fa47dbc Mon Sep 17 00:00:00 2001
From: CPWstatic <13495049+CPWstatic@users.noreply.github.com>
Date: Tue, 19 Nov 2019 10:56:57 +0800
Subject: [PATCH] Check variable existence and modify doc. (#1151)

---
 .../fetch-syntax.md                                 |  2 +-
 .../fetch-syntax.md                                 |  2 +-
 src/graph/FetchEdgesExecutor.cpp                    | 13 +++++++------
 src/graph/FetchVerticesExecutor.cpp                 | 11 ++++++-----
 4 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/docs/manual-CN/2.query-language/4.statement-syntax/2.data-query-and-manipulation-statements/fetch-syntax.md b/docs/manual-CN/2.query-language/4.statement-syntax/2.data-query-and-manipulation-statements/fetch-syntax.md
index 14019564527..36a61e8d9e0 100644
--- a/docs/manual-CN/2.query-language/4.statement-syntax/2.data-query-and-manipulation-statements/fetch-syntax.md
+++ b/docs/manual-CN/2.query-language/4.statement-syntax/2.data-query-and-manipulation-statements/fetch-syntax.md
@@ -27,7 +27,7 @@ nebula> FETCH PROP ON player 1 YIELD player.name, player.age
 nebula> FETCH PROP ON player hash(\"nebula\")  YIELD player.name, player.age
 -- 沿边 e1 寻找节点 1 的所有近邻，返回其姓名和年龄属性
 nebula> GO FROM 1 over e1 YIELD e1._dst AS id | FETCH PROP ON player $-.id YIELD player.name, player.age
--- 与上述语句相同
+-- 与上述语法相同
 nebula> $var = GO FROM 1 over e1 YIELD e1._dst AS id; FETCH PROP ON player $var.id YIELD player.name, player.age
 -- 获取 1，2，3 三个节点，返回姓名和年龄都不相同的记录
 nebula> FETCH PROP ON player 1,2,3 YIELD DISTINCT player.name, player.age
diff --git a/docs/manual-EN/2.query-language/4.statement-syntax/2.data-query-and-manipulation-statements/fetch-syntax.md b/docs/manual-EN/2.query-language/4.statement-syntax/2.data-query-and-manipulation-statements/fetch-syntax.md
index da417bedd03..767c3be1ffa 100644
--- a/docs/manual-EN/2.query-language/4.statement-syntax/2.data-query-and-manipulation-statements/fetch-syntax.md
+++ b/docs/manual-EN/2.query-language/4.statement-syntax/2.data-query-and-manipulation-statements/fetch-syntax.md
@@ -4,7 +4,7 @@ The `FETCH` syntax is used to get vertex/edge's properties.
 
 ## Fetch Vertex property
 
-Use `FETCH PROP ON` to return a (list of) vertex's properties. Currently, you can get multiple vertices' properties with the same tag in one sentence.  
+Use `FETCH PROP ON` to return a (list of) vertex's properties. Currently, you can get multiple vertices' properties with the same tag in one sentence.
 
 ```ngql
 FETCH PROP ON <tag_name> <vertex_id_list> [YIELD [DISTINCT] <return_list>]
diff --git a/src/graph/FetchEdgesExecutor.cpp b/src/graph/FetchEdgesExecutor.cpp
index 119a0a4e68c..63e11b7c39c 100644
--- a/src/graph/FetchEdgesExecutor.cpp
+++ b/src/graph/FetchEdgesExecutor.cpp
@@ -143,16 +143,17 @@ Status FetchEdgesExecutor::setupEdgeKeysFromRef() {
     const InterimResult *inputs;
     if (sentence_->ref()->isInputExpr()) {
         inputs = inputs_.get();
-        if (inputs == nullptr || !inputs->hasData()) {
-            // we have empty imputs from pipe.
-            return Status::OK();
-        }
     } else {
-        inputs = ectx()->variableHolder()->get(varname_);
-        if (inputs == nullptr || !inputs->hasData()) {
+        bool existing = false;
+        inputs = ectx()->variableHolder()->get(varname_, &existing);
+        if (!existing) {
             return Status::Error("Variable `%s' not defined", varname_.c_str());
         }
     }
+    if (inputs == nullptr || !inputs->hasData()) {
+        // we have empty imputs from pipe.
+        return Status::OK();
+    }
 
     auto ret = inputs->getVIDs(*srcid_);
     if (!ret.ok()) {
diff --git a/src/graph/FetchVerticesExecutor.cpp b/src/graph/FetchVerticesExecutor.cpp
index d1929abd2b5..8d9e248c7d6 100644
--- a/src/graph/FetchVerticesExecutor.cpp
+++ b/src/graph/FetchVerticesExecutor.cpp
@@ -286,15 +286,16 @@ Status FetchVerticesExecutor::setupVidsFromRef() {
     const InterimResult *inputs;
     if (varname_ == nullptr) {
         inputs = inputs_.get();
-        if (inputs == nullptr || !inputs->hasData()) {
-            return Status::OK();
-        }
     } else {
-        inputs = ectx()->variableHolder()->get(*varname_);
-        if (inputs == nullptr || !inputs->hasData()) {
+        bool existing = false;
+        inputs = ectx()->variableHolder()->get(*varname_, &existing);
+        if (!existing) {
             return Status::Error("Variable `%s' not defined", varname_->c_str());
         }
     }
+    if (inputs == nullptr || !inputs->hasData()) {
+        return Status::OK();
+    }
 
     StatusOr<std::vector<VertexID>> result;
     if (distinct_) {