*: improve region path

server/storage/endpoint/key_path.go

@@ -17,6 +17,8 @@ package endpoint
 import (
 	"fmt"
 	"path"
+	"strconv"
+	"strings"
 )
 
 const (
@@ -38,6 +40,7 @@ const (
 	keyspaceMetaInfix          = "meta"
 	keyspaceIDInfix            = "id"
 	keyspaceAllocID            = "alloc_id"
+	regionPathPrefix           = "raft/r"
 )
 
 // AppendToRootPath appends the given key to the rootPath.
@@ -74,7 +77,27 @@ func storeRegionWeightPath(storeID uint64) string {
 
 // RegionPath returns the region meta info key path with the given region ID.
 func RegionPath(regionID uint64) string {
-	return path.Join(clusterPath, "r", fmt.Sprintf("%020d", regionID))
+	var buf strings.Builder
+	buf.WriteString(regionPathPrefix)
+	buf.WriteString("/")
+	s := strconv.FormatUint(regionID, 10)
+	if len(s) > 20 {
+		s = s[len(s)-20:]
+	} else {
+		b := make([]byte, 20)
+		diff := 20 - len(s)
+		for i := 0; i < 20; i++ {
+			if i < diff {
+				b[i] = 48
+			} else {
+				b[i] = s[i-diff]
+			}
+		}
+		s = string(b)
+	}
+	buf.WriteString(s)
+
+	return buf.String()
 }
 
 func ruleKeyPath(ruleKey string) string {

server/storage/endpoint/key_path_test.go

@@ -0,0 +1,29 @@
+package endpoint
+
+import (
+	"fmt"
+	"math/rand"
+	"path"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestRegionPath(t *testing.T) {
+	re := require.New(t)
+	f := func(id uint64) string {
+		return path.Join(regionPathPrefix, fmt.Sprintf("%020d", id))
+	}
+	rand.Seed(time.Now().Unix())
+	for i := 0; i < 1000; i++ {
+		id := rand.Uint64()
+		re.Equal(f(id), RegionPath(id))
+	}
+}
+
+func BenchmarkRegionPath(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		_ = RegionPath(uint64(i))
+	}
+}