type: add db prefix to function name for not exist error messages

executor/aggregate_test.go

@@ -343,7 +343,7 @@ func (s *testSuite1) TestAggregation(c *C) {
 	c.Assert(errors.Cause(err).Error(), Equals, "unsupported agg function: stddev_pop")
 	_, err = tk.Exec("select std_samp(a) from t")
 	// TODO: Fix this error message.
-	c.Assert(errors.Cause(err).Error(), Equals, "[expression:1305]FUNCTION std_samp does not exist")
+	c.Assert(errors.Cause(err).Error(), Equals, "[expression:1305]FUNCTION test.std_samp does not exist")
 	_, err = tk.Exec("select variance(a) from t")
 	// TODO: Fix this error message.
 	c.Assert(errors.Cause(err).Error(), Equals, "unsupported agg function: var_pop")

expression/integration_test.go

@@ -4921,3 +4921,23 @@ func (s *testIntegrationSuite) TestIssue11309And11319(c *C) {
 	tk.MustQuery(`SELECT DATE_ADD('2007-03-28 22:08:28',INTERVAL 2.2 DAY_HOUR)`).Check(testkit.Rows("2007-03-31 00:08:28"))
 	tk.MustQuery(`SELECT DATE_ADD('2007-03-28 22:08:28',INTERVAL 2.2 YEAR_MONTH)`).Check(testkit.Rows("2009-05-28 22:08:28"))
 }
+
+func (s *testIntegrationSuite) TestNotExistFunc(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+
+	// current db is empty
+	_, err := tk.Exec("SELECT xxx(1)")
+	c.Assert(err.Error(), Equals, "[planner:1046]No database selected")
+
+	_, err = tk.Exec("SELECT yyy()")
+	c.Assert(err.Error(), Equals, "[planner:1046]No database selected")
+
+	// current db is not empty
+	tk.MustExec("use test")
+	_, err = tk.Exec("SELECT xxx(1)")
+	c.Assert(err.Error(), Equals, "[expression:1305]FUNCTION test.xxx does not exist")
+
+	_, err = tk.Exec("SELECT yyy()")
+	c.Assert(err.Error(), Equals, "[expression:1305]FUNCTION test.yyy does not exist")
+
+}

expression/scalar_function.go

@@ -120,7 +120,12 @@ func newFunctionImpl(ctx sessionctx.Context, fold bool, funcName string, retType
 	}
 	fc, ok := funcs[funcName]
 	if !ok {
-		return nil, errFunctionNotExists.GenWithStackByArgs("FUNCTION", funcName)
+		db := ctx.GetSessionVars().CurrentDB
+		if db == "" {
+			return nil, terror.ClassOptimizer.New(mysql.ErrNoDB, mysql.MySQLErrName[mysql.ErrNoDB])
+		}
+
+		return nil, errFunctionNotExists.GenWithStackByArgs("FUNCTION", db+"."+funcName)
 	}
 	if !ctx.GetSessionVars().EnableNoopFuncs {
 		if _, ok := noopFuncs[funcName]; ok {