executor,types: Fix truncate function behavior when second param is large negative (pingcap#53075)

close pingcap#52978

Author: yibin87

pkg/executor/test/issuetest/BUILD.bazel

@@ -8,7 +8,7 @@ go_test(
         "main_test.go",
     ],
     flaky = True,
-    shard_count = 17,
+    shard_count = 18,
     deps = [
         "//pkg/autoid_service",
         "//pkg/config",

pkg/executor/test/issuetest/executor_issue_test.go

@@ -635,3 +635,15 @@ func TestIssue51874(t *testing.T) {
 	tk.MustExec("insert into t2 values (10), (100)")
 	tk.MustQuery("select (select sum(a) over () from t2 limit 1) from t;").Check(testkit.Rows("10", "2"))
 }
+
+func TestIssue52978(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t (a int)")
+	tk.MustExec("insert into t values (-1790816583),(2049821819), (-1366665321), (536581933), (-1613686445)")
+	tk.MustQuery("select min(truncate(cast(-26340 as double), ref_11.a)) as c3 from t as ref_11;").Check(testkit.Rows("-26340"))
+	tk.MustExec("drop table if exists t")
+}

pkg/types/helper.go

@@ -58,6 +58,12 @@ func Truncate(f float64, dec int) float64 {
 	if math.IsInf(tmp, 0) {
 		return f
 	}
+	if shift == 0.0 {
+		if math.IsNaN(f) {
+			return f
+		}
+		return 0.0
+	}
 	return math.Trunc(tmp) / shift
 }
 

pkg/types/helper_test.go

@@ -52,6 +52,8 @@ func TestTruncate(t *testing.T) {
 		{123.45, 1, 123.4},
 		{123.45, 2, 123.45},
 		{123.45, 3, 123.450},
+		{123.45, -400, 0.0},
+		{123.45, 400, 123.45},
 	}
 	for _, tt := range tests {
 		res := Truncate(tt.f, tt.dec)