sort mariadb gtid set

mysql/mariadb_gtid.go

@@ -3,6 +3,7 @@ package mysql
 import (
 	"bytes"
 	"fmt"
+	"sort"
 	"strconv"
 	"strings"
 
@@ -157,7 +158,26 @@ func (s *MariadbGTIDSet) Update(GTIDStr string) error {
 }
 
 func (s *MariadbGTIDSet) String() string {
-	return hack.String(s.Encode())
+	if len(s.Sets) == 1 {
+		for _, set := range s.Sets {
+			return set.String()
+		}
+	}
+
+	var buf bytes.Buffer
+	sets := make([]string, 0, len(s.Sets))
+	for _, set := range s.Sets {
+		sets = append(sets, set.String())
+	}
+	sort.Strings(sets)
+
+	sep := ""
+	for _, set := range sets {
+		buf.WriteString(sep)
+		buf.WriteString(set)
+		sep = ","
+	}
+	return hack.String(buf.Bytes())
 }
 
 // Encode encodes mariadb gtid set

mysql/mariadb_gtid_test.go

@@ -232,3 +232,12 @@ func (t *mariaDBTestSuite) TestMariaDBGTIDSetClone(c *check.C) {
 		c.Assert(gtidSet.Clone(), check.DeepEquals, gtidSet)
 	}
 }
+
+func (t *mariaDBTestSuite) TestMariaDBGTIDSetSortedString(c *check.C) {
+	gtidSetStr := "2-2-2,1-1-1,3-2-1"
+	sorted := "1-1-1,2-2-2,3-2-1"
+
+	gtidSet, err := ParseMariadbGTIDSet(gtidSetStr)
+	c.Assert(err, check.IsNil)
+	c.Assert(gtidSet.String(), check.Equals, sorted)
+}