sessionctx: add 'time_zone' session variable (#2375)

sessionctx/variable/session.go

@@ -16,6 +16,7 @@ package variable
 import (
 	"strings"
 	"sync"
+	"time"
 
 	"github.com/juju/errors"
 	"github.com/pingcap/tidb/mysql"
@@ -144,6 +145,10 @@ type SessionVars struct {
 	// CurrInsertValues is used to record current ValuesExpr's values.
 	// See http://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_values
 	CurrInsertValues interface{}
+
+	// Per-connection time zones. Each client that connects has its own time zone setting, given by the session time_zone variable.
+	// See https://dev.mysql.com/doc/refman/5.7/en/time-zone-support.html
+	TimeZone *time.Location
 }
 
 // NewSessionVars creates a session vars object.
@@ -224,6 +229,7 @@ const (
 	SQLModeVar          = "sql_mode"
 	AutocommitVar       = "autocommit"
 	CharacterSetResults = "character_set_results"
+	TimeZone            = "time_zone"
 )
 
 // GetTiDBSystemVar gets variable value for name.

sessionctx/varsutil/varsutil.go

@@ -85,6 +85,8 @@ func SetSessionSystemVar(vars *variable.SessionVars, name string, value types.Da
 		return errors.Trace(err)
 	}
 	switch name {
+	case variable.TimeZone:
+		vars.TimeZone = parseTimeZone(sVal)
 	case variable.SQLModeVar:
 		sVal = strings.ToUpper(sVal)
 		if strings.Contains(sVal, "STRICT_TRANS_TABLES") || strings.Contains(sVal, "STRICT_ALL_TABLES") {
@@ -112,6 +114,28 @@ func SetSessionSystemVar(vars *variable.SessionVars, name string, value types.Da
 	return nil
 }
 
+func parseTimeZone(s string) *time.Location {
+	if s == "SYSTEM" {
+		// TODO: Support global time_zone variable, it should be set to global time_zone value.
+		return time.Local
+	}
+
+	loc, err := time.LoadLocation(s)
+	if err == nil {
+		return loc
+	}
+
+	// The value can be given as a string indicating an offset from UTC, such as '+10:00' or '-6:00'.
+	if strings.HasPrefix(s, "+") || strings.HasPrefix(s, "-") {
+		d, err := types.ParseDuration(s[1:], 0)
+		if err == nil {
+			return time.FixedZone("UTC", int(d.Duration/time.Second))
+		}
+	}
+
+	return nil
+}
+
 func setSnapshotTS(s *variable.SessionVars, sVal string) error {
 	if sVal == "" {
 		s.SnapshotTS = 0

sessionctx/varsutil/varsutil_test.go

@@ -15,6 +15,7 @@ package varsutil
 
 import (
 	"testing"
+	"time"
 
 	. "github.com/pingcap/check"
 	"github.com/pingcap/tidb/sessionctx/variable"
@@ -57,7 +58,7 @@ func (s *testVarsutilSuite) TestVarsutil(c *C) {
 
 	c.Assert(SetSessionSystemVar(v, "character_set_results", types.Datum{}), IsNil)
 
-	// Test case for get TiDBSkipConstraintCheck session variable
+	// Test case for get TiDBSkipConstraintCheck session variable.
 	val, err = GetSessionSystemVar(v, variable.TiDBSkipConstraintCheck)
 	c.Assert(err, IsNil)
 	c.Assert(val, Equals, "0")
@@ -77,7 +78,7 @@ func (s *testVarsutilSuite) TestVarsutil(c *C) {
 	c.Assert(err, IsNil)
 	c.Assert(val, Equals, "1")
 
-	// Test case for get TiDBSkipDDLWait session variable
+	// Test case for get TiDBSkipDDLWait session variable.
 	val, err = GetSessionSystemVar(v, variable.TiDBSkipDDLWait)
 	c.Assert(val, Equals, "0")
 	c.Assert(v.SkipDDLWait, IsFalse)
@@ -87,4 +88,19 @@ func (s *testVarsutilSuite) TestVarsutil(c *C) {
 	c.Assert(v.SkipDDLWait, IsTrue)
 	val, err = GetSessionSystemVar(v, variable.TiDBSkipDDLWait)
 	c.Assert(val, Equals, "1")
+
+	// Test case for time_zone session variable.
+	SetSessionSystemVar(v, variable.TimeZone, types.NewStringDatum("Europe/Helsinki"))
+	c.Assert(v.TimeZone.String(), Equals, "Europe/Helsinki")
+	SetSessionSystemVar(v, variable.TimeZone, types.NewStringDatum("US/Eastern"))
+	c.Assert(v.TimeZone.String(), Equals, "US/Eastern")
+	SetSessionSystemVar(v, variable.TimeZone, types.NewStringDatum("SYSTEM"))
+	c.Assert(v.TimeZone.String(), Equals, "Local")
+	SetSessionSystemVar(v, variable.TimeZone, types.NewStringDatum("+10:00"))
+	c.Assert(v.TimeZone.String(), Equals, "UTC")
+	t1 := time.Date(2000, 1, 1, 0, 0, 0, 0, v.TimeZone)
+	t2 := time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)
+	c.Assert(t2.Sub(t1), Equals, 10*time.Hour)
+	SetSessionSystemVar(v, variable.TimeZone, types.NewStringDatum("-6:00"))
+	c.Assert(v.TimeZone.String(), Equals, "UTC")
 }