sessionctx: supports set character_set_results = null (#7353)

pingcap · Aug 11, 2018 · 8762592 · 8762592
1 parent 51e86a3
commit 8762592
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Showing 2 changed files with 6 additions and 6 deletions.
diff --git a/executor/set_test.go b/executor/set_test.go
@@ -133,7 +133,8 @@ func (s *testSuite) TestSetVar(c *C) {
 	c.Assert(charset, Equals, "utf8")
 	c.Assert(collation, Equals, "utf8_bin")
 
-	tk.MustExec("set @@character_set_results = NULL")
+	tk.MustExec("set character_set_results = NULL")
+	tk.MustQuery("select @@character_set_results").Check(testkit.Rows(""))
 
 	// Test set transaction isolation level, which is equivalent to setting variable "tx_isolation".
 	tk.MustExec("SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED")

diff --git a/sessionctx/variable/varsutil.go b/sessionctx/variable/varsutil.go
@@ -127,12 +127,11 @@ func SetSessionSystemVar(vars *SessionVars, name string, value types.Datum) erro
 	if sysVar == nil {
 		return UnknownSystemVar
 	}
-	if value.IsNull() {
-		return vars.deleteSystemVar(name)
-	}
-	var sVal string
+	sVal := ""
 	var err error
-	sVal, err = value.ToString()
+	if !value.IsNull() {
+		sVal, err = value.ToString()
+	}
 	if err != nil {
 		return errors.Trace(err)
 	}