From 024d4dde2016e549341b401038e35537c0f5e684 Mon Sep 17 00:00:00 2001
From: HuaiyuXu <391585975@qq.com>
Date: Mon, 21 Aug 2017 20:38:46 +0800
Subject: [PATCH] expression: fix a bug when datum.kind is not consistent with
 expression.type (#4269)

---
 expression/expression.go       | 6 ++++--
 expression/integration_test.go | 2 ++
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/expression/expression.go b/expression/expression.go
index e22cdb118d..a16f544abe 100644
--- a/expression/expression.go
+++ b/expression/expression.go
@@ -177,7 +177,9 @@ func evalExprToReal(expr Expression, row []types.Datum, sc *variable.StatementCo
 		return res, val.IsNull(), errors.Trace(err)
 	}
 	if expr.GetTypeClass() == types.ClassReal {
-		return val.GetFloat64(), false, nil
+		// TODO: fix this to val.GetFloat64() after all built-in functions been rewritten.
+		res, err = val.ToFloat64(sc)
+		return res, false, errors.Trace(err)
 	} else if IsHybridType(expr) {
 		res, err = val.ToFloat64(sc)
 		return res, false, errors.Trace(err)
@@ -200,7 +202,7 @@ func evalExprToDecimal(expr Expression, row []types.Datum, sc *variable.Statemen
 		// we infer the result type of the sql as `mysql.TypeNewDecimal` which is consistent with MySQL,
 		// but what we actually get is store as float64 in Datum.
 		// So if we wrap `CastDecimalAsInt` upon the result, we'll get <nil> when call `arg.EvalDecimal()`.
-		// This will be fixed after all built-in functions be rewrite correctlly.
+		// This will be fixed after all built-in functions be rewrite correctly.
 	} else if IsHybridType(expr) {
 		res, err = val.ToDecimal(sc)
 		return res, false, errors.Trace(err)
diff --git a/expression/integration_test.go b/expression/integration_test.go
index cc7b91051a..325b960352 100644
--- a/expression/integration_test.go
+++ b/expression/integration_test.go
@@ -1525,6 +1525,8 @@ func (s *testIntegrationSuite) TestControlBuiltin(c *C) {
 	result = tk.MustQuery("SELECT 79 + + + CASE -87 WHEN -30 THEN COALESCE(COUNT(*), +COALESCE(+15, -33, -12 ) + +72) WHEN +COALESCE(+AVG(DISTINCT(60)), 21) THEN NULL ELSE NULL END AS col0;")
 	result.Check(testkit.Rows("<nil>"))
 
+	result = tk.MustQuery("SELECT -63 + COALESCE ( - 83, - 61 + - + 72 * - CAST( NULL AS SIGNED ) + + 3 );")
+	result.Check(testkit.Rows("-146"))
 }
 
 func (s *testIntegrationSuite) TestArithmeticBuiltin(c *C) {