From b211a2724f728948957e8267ee9d722e325cd801 Mon Sep 17 00:00:00 2001
From: ti-srebot <66930949+ti-srebot@users.noreply.github.com>
Date: Thu, 10 Nov 2022 14:51:52 +0800
Subject: [PATCH] expression: adjust DST for convert_tz() (#37206) (#37953)

close pingcap/tidb#30081
---
 expression/builtin_time.go      |  2 +-
 expression/builtin_time_test.go |  2 +-
 expression/integration_test.go  | 11 +++++++++++
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/expression/builtin_time.go b/expression/builtin_time.go
index ef387deb6cacb..9901b9323d060 100644
--- a/expression/builtin_time.go
+++ b/expression/builtin_time.go
@@ -5932,7 +5932,7 @@ func (b *builtinConvertTzSig) convertTz(dt types.Time, fromTzStr, toTzStr string
 		}
 	}
 
-	t, err := dt.GoTime(fromTz)
+	t, err := dt.AdjustedGoTime(fromTz)
 	if err != nil {
 		return types.ZeroTime, true, nil
 	}
diff --git a/expression/builtin_time_test.go b/expression/builtin_time_test.go
index 703d6f38160d5..2fcf98d3db3d8 100644
--- a/expression/builtin_time_test.go
+++ b/expression/builtin_time_test.go
@@ -2725,7 +2725,7 @@ func TestConvertTz(t *testing.T) {
 		{"2021-10-31 02:59:59", "Europe/Amsterdam", "+02:00", true, "2021-10-31 03:59:59"},
 		{"2021-10-31 02:00:00", "Europe/Amsterdam", "+01:00", true, "2021-10-31 02:00:00"},
 		{"2021-10-31 03:00:00", "Europe/Amsterdam", "+01:00", true, "2021-10-31 03:00:00"},
-		{"2021-03-28 02:30:00", "Europe/Amsterdam", "UTC", true, ""},
+		{"2021-03-28 02:30:00", "Europe/Amsterdam", "UTC", true, "2021-03-28 01:00:00"},
 		{"2021-10-22 10:00:00", "Europe/Tallinn", "SYSTEM", true, t1.In(loc2).Format("2006-01-02 15:04:00")},
 		{"2021-10-22 10:00:00", "SYSTEM", "Europe/Tallinn", true, t2.In(loc1).Format("2006-01-02 15:04:00")},
 	}
diff --git a/expression/integration_test.go b/expression/integration_test.go
index d80c53d9fa2a1..b3aa0c84f7195 100644
--- a/expression/integration_test.go
+++ b/expression/integration_test.go
@@ -6920,6 +6920,17 @@ func TestIssue28739(t *testing.T) {
 		"<nil> <nil>"))
 }
 
+func TestIssue30081(t *testing.T) {
+	store, clean := testkit.CreateMockStore(t)
+	defer clean()
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec(`USE test`)
+	tk.MustQuery(`SELECT CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central');`).
+		Check(testkit.Rows(`2007-03-11 01:00:00`))
+	tk.MustQuery(`SELECT CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central');`).
+		Check(testkit.Rows(`2007-03-11 01:00:00`))
+}
+
 func TestIssue30326(t *testing.T) {
 	store, clean := testkit.CreateMockStore(t)
 	defer clean()