From ec6a822cfa782c744415d5b47341ae969b0852c4 Mon Sep 17 00:00:00 2001
From: zhexuany <yangzhexuan@pingcap.com>
Date: Fri, 7 Sep 2018 12:42:48 +0800
Subject: [PATCH] get tz name from zoneinfo

---
 executor/distsql.go                         | 16 +++++++++++++++-
 executor/distsql_test.go                    |  6 ++++++
 store/mockstore/mocktikv/cop_handler_dag.go | 15 +++++++++++++++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/executor/distsql.go b/executor/distsql.go
index b16c04aad1901..e1f8c11a937ef 100644
--- a/executor/distsql.go
+++ b/executor/distsql.go
@@ -117,6 +117,16 @@ func closeAll(objs ...Closeable) error {
 	return errors.Trace(err)
 }
 
+func getTZNameFromFileName(path string) (string, error) {
+	// phase1 only support read /etc/localtime which is a softlink to zoneinfo file
+	substr := "share/zoneinfo"
+	if strings.Contains(path, substr) {
+		idx := strings.Index(path, substr)
+		return string(path[idx+len(substr)+1:]), nil
+	}
+	return "", errors.New("only support softlink has share/zoneinfo as a suffix" + path)
+}
+
 // zone returns the current timezone name and timezone offset in seconds.
 // In compatible with MySQL, we change `Local` to `System`.
 // TODO: Golang team plan to return system timezone name intead of
@@ -127,7 +137,11 @@ func zone(sctx sessionctx.Context) (string, int64) {
 	var name string
 	name = loc.String()
 	if name == "Local" {
-		name = "System"
+		path, err := filepath.EvalSymlinks("/etc/localtime")
+		if err != nil {
+			return "Sysytem", int64(offset)
+		}
+		return getTZNameFromFileName(path), int64(offset)
 	}
 
 	return name, int64(offset)
diff --git a/executor/distsql_test.go b/executor/distsql_test.go
index 070c10233e1be..15edf80a586a4 100644
--- a/executor/distsql_test.go
+++ b/executor/distsql_test.go
@@ -207,3 +207,9 @@ func (s *testSuite) TestUniqueKeyNullValueSelect(c *C) {
 	res = tk.MustQuery("select * from t where id is null;")
 	res.Check(testkit.Rows("<nil> a", "<nil> b", "<nil> c"))
 }
+
+func (s *testSuite) TestgetTZNameFromFileName(c *C) {
+	tz, err := getTZNameFromFileName("/user/share/zoneinfo/Asia/Shanghai")
+	c.Assert(err, IsNil)
+	c.Assert(tz, Equals, "Asia/Shanghai")
+}
diff --git a/store/mockstore/mocktikv/cop_handler_dag.go b/store/mockstore/mocktikv/cop_handler_dag.go
index 456e1feb057b2..450694703573d 100644
--- a/store/mockstore/mocktikv/cop_handler_dag.go
+++ b/store/mockstore/mocktikv/cop_handler_dag.go
@@ -17,6 +17,7 @@ import (
 	"bytes"
 	"fmt"
 	"io"
+	"strings"
 	"sync"
 	"time"
 
@@ -41,6 +42,7 @@ import (
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/metadata"
+	"path/filepath"
 )
 
 var dummySlice = make([]byte, 0)
@@ -164,13 +166,26 @@ func (h *rpcHandler) buildDAGExecutor(req *coprocessor.Request) (*dagContext, ex
 	return ctx, e, dagReq, err
 }
 
+func getTZNameFromFileName(path string) (string, error) {
+	// phase1 only support read /etc/localtime which is a softlink to zoneinfo file
+	substr := "share/zoneinfo"
+	if strings.Contains(path, substr) {
+		idx := strings.Index(path, substr)
+		return string(path[idx+len(substr)+1:]), nil
+	}
+	return "", errors.New("only support softlink has share/zoneinfo as a suffix" + path)
+}
+
 // constructTimeZone constructs timezone by name first. When the timezone name
 // is set, the daylight saving problem must be considered. Otherwise the
 // timezone offset in seconds east of UTC is used to constructed the timezone.
 func constructTimeZone(name string, offset int) (*time.Location, error) {
 	if name != "" {
+		// no need to care about case since name is retreved
+		// from go std library call
 		return LocCache.getLoc(name)
 	}
+
 	return time.FixedZone("", offset), nil
 }