From 738f933016c27feaddf589335cc6ed735acba03a Mon Sep 17 00:00:00 2001
From: HuaiyuXu <391585975@qq.com>
Date: Wed, 6 Dec 2017 13:17:29 +0800
Subject: [PATCH] *: session variable value should not be modified when get
 global variable (#5317)

---
 new_session_test.go             | 11 +++++++++++
 sessionctx/varsutil/varsutil.go |  1 -
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/new_session_test.go b/new_session_test.go
index 06a8709cd4335..a0bd7fa34bd6c 100644
--- a/new_session_test.go
+++ b/new_session_test.go
@@ -296,6 +296,17 @@ func (s *testSessionSuite) TestGlobalVarAccessor(c *C) {
 	result.Check(testkit.Rows("sql_select_limit 18446744073709551615"))
 	result = tk.MustQuery("show session variables where variable_name='sql_select_limit';")
 	result.Check(testkit.Rows("sql_select_limit 100000000000"))
+
+	result = tk.MustQuery("select @@global.autocommit;")
+	result.Check(testkit.Rows("ON"))
+	result = tk.MustQuery("select @@autocommit;")
+	result.Check(testkit.Rows("ON"))
+	tk.MustExec("set @@global.autocommit = 0;")
+	result = tk.MustQuery("select @@global.autocommit;")
+	result.Check(testkit.Rows("0"))
+	result = tk.MustQuery("select @@autocommit;")
+	result.Check(testkit.Rows("ON"))
+	tk.MustExec("set @@global.autocommit=1")
 }
 
 func (s *testSessionSuite) TestRetryResetStmtCtx(c *C) {
diff --git a/sessionctx/varsutil/varsutil.go b/sessionctx/varsutil/varsutil.go
index d6417e495e1f8..251e990406ce0 100644
--- a/sessionctx/varsutil/varsutil.go
+++ b/sessionctx/varsutil/varsutil.go
@@ -76,7 +76,6 @@ func GetGlobalSystemVar(s *variable.SessionVars, key string) (string, error) {
 	if err != nil {
 		return "", errors.Trace(err)
 	}
-	s.Systems[key] = gVal
 	return gVal, nil
 }