*: fix union result when mix signed/unsigned columns

executor/executor_test.go

@@ -2919,3 +2919,31 @@ func (s *testSuite) TestIndexJoinTableDualPanic(c *C) {
 	tk.MustQuery("select a.* from a inner join (select 1 as k1,'k2-1' as k2) as k on a.f1=k.k1;").
 		Check(testkit.Rows("1 a"))
 }
+
+func (s *testSuite) TestUnionAutoSignedCast(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t1,t2")
+	tk.MustExec("create table t1 (id int, i int, b bigint, d double, dd decimal)")
+	tk.MustExec("create table t2 (id int, i int unsigned, b bigint unsigned, d double unsigned, dd decimal unsigned)")
+	tk.MustExec("insert into t1 values(1, -1, -1, -1.1, -1)")
+	tk.MustExec("insert into t2 values(2, 1, 1, 1.1, 1)")
+	tk.MustQuery("select * from t1 union select * from t2 order by id").
+		Check(testkit.Rows("1 -1 -1 -1.1 -1", "2 1 1 1.1 1"))
+	tk.MustQuery("select id, i, b, d, dd from t2 union select id, i, b, d, dd from t1 order by id").
+		Check(testkit.Rows("1 0 0 0 -1", "2 1 1 1.1 1"))
+	tk.MustQuery("select id, i from t2 union select id, cast(i as unsigned int) from t1 order by id").
+		Check(testkit.Rows("1 18446744073709551615", "2 1"))
+	tk.MustQuery("select dd from t2 union all select dd from t2").
+		Check(testkit.Rows("1", "1"))
+
+	tk.MustExec("drop table if exists t3,t4")
+	tk.MustExec("create table t3 (id int, v int)")
+	tk.MustExec("create table t4 (id int, v double unsigned)")
+	tk.MustExec("insert into t3 values (1, -1)")
+	tk.MustExec("insert into t4 values (2, 1)")
+	tk.MustQuery("select id, v from t3 union select id, v from t4 order by id").
+		Check(testkit.Rows("1 -1", "2 1"))
+	tk.MustQuery("select id, v from t4 union select id, v from t3 order by id").
+		Check(testkit.Rows("1 0", "2 1"))
+}

expression/builtin.go

@@ -236,6 +236,26 @@ func (b *baseBuiltinFunc) Clone() builtinFunc {
 	panic("you should not call this method.")
 }
 
+// baseBuiltinCastFunc will be contained in every struct that implement cast builtinFunc.
+type baseBuiltinCastFunc struct {
+	baseBuiltinFunc
+
+	// inUnion indicates whether cast is in union context.
+	inUnion bool
+}
+
+func (b *baseBuiltinCastFunc) cloneFrom(from *baseBuiltinCastFunc) {
+	b.baseBuiltinFunc.cloneFrom(&from.baseBuiltinFunc)
+	b.inUnion = from.inUnion
+}
+
+func newBaseBuiltinCastFunc(builtinFunc baseBuiltinFunc, inUnion bool) baseBuiltinCastFunc {
+	return baseBuiltinCastFunc{
+		baseBuiltinFunc: builtinFunc,
+		inUnion:         inUnion,
+	}
+}
+
 // builtinFunc stands for a particular function signature.
 type builtinFunc interface {
 	// evalInt evaluates int result of builtinFunc by given row.