expression: fix wrong result of greatest/least(mixed unsigned/signed int)

expression/builtin_compare.go

@@ -478,6 +478,13 @@ func (c *greatestFunctionClass) getFunction(ctx sessionctx.Context, args []Expre
 	}
 	switch tp {
 	case types.ETInt:
+		//default signed, if one field is unsigned, return unsigned result
+		for _, arg := range args {
+			if mysql.HasUnsignedFlag(arg.GetType().Flag) {
+				bf.tp.Flag |= mysql.UnsignedFlag
+				break
+			}
+		}
 		sig = &builtinGreatestIntSig{bf}
 		sig.setPbCode(tipb.ScalarFuncSig_GreatestInt)
 	case types.ETReal:
@@ -745,6 +752,14 @@ func (c *leastFunctionClass) getFunction(ctx sessionctx.Context, args []Expressi
 	}
 	switch tp {
 	case types.ETInt:
+		// default unsigned, if one field is signed, return signed result
+		bf.tp.Flag |= mysql.UnsignedFlag
+		for _, arg := range args {
+			if !mysql.HasUnsignedFlag(arg.GetType().Flag) {
+				bf.tp.Flag &= ^mysql.UnsignedFlag
+				break
+			}
+		}
 		sig = &builtinLeastIntSig{bf}
 		sig.setPbCode(tipb.ScalarFuncSig_LeastInt)
 	case types.ETReal:

expression/builtin_compare_test.go

@@ -279,6 +279,8 @@ func TestGreatestLeastFunc(t *testing.T) {
 	sc := ctx.GetSessionVars().StmtCtx
 	originIgnoreTruncate := sc.IgnoreTruncate
 	sc.IgnoreTruncate = true
+	decG := &types.MyDecimal{}
+	decL := &types.MyDecimal{}
 	defer func() {
 		sc.IgnoreTruncate = originIgnoreTruncate
 	}()
@@ -290,6 +292,14 @@ func TestGreatestLeastFunc(t *testing.T) {
 		isNil            bool
 		getErr           bool
 	}{
+		{
+			[]interface{}{int64(-9223372036854775808), uint64(9223372036854775809)},
+			decG.FromUint(9223372036854775809), decL.FromInt(-9223372036854775808), false, false,
+		},
+		{
+			[]interface{}{uint64(9223372036854775808), uint64(9223372036854775809)},
+			uint64(9223372036854775809), uint64(9223372036854775808), false, false,
+		},
 		{
 			[]interface{}{1, 2, 3, 4},
 			int64(4), int64(1), false, false,

expression/integration_test.go

@@ -10644,3 +10644,12 @@ func (s *testIntegrationSuite) TestIssue29513(c *C) {
 	tk.MustQuery("select '123' union select cast(a as char) from t;").Sort().Check(testkit.Rows("123", "45678"))
 	tk.MustQuery("select '123' union select cast(a as char(2)) from t;").Sort().Check(testkit.Rows("123", "45"))
 }
+
+func (s *testIntegrationSuite) TestIssue30101(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t1;")
+	tk.MustExec("create table t1(c1 bigint unsigned, c2 bigint unsigned);")
+	tk.MustExec("insert into t1 values(9223372036854775808, 9223372036854775809);")
+	tk.MustQuery("select greatest(c1, c2) from t1;").Sort().Check(testkit.Rows("9223372036854775809"))
+}