bugfix: handle the reply of select command

internal/writer/redis.go

@@ -9,6 +9,7 @@ import (
 	"github.com/alibaba/RedisShake/internal/log"
 	"github.com/alibaba/RedisShake/internal/statistics"
 	"strconv"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -57,6 +58,10 @@ func (w *redisWriter) Write(e *entry.Entry) {
 func (w *redisWriter) switchDbTo(newDbId int) {
 	w.client.Send("select", strconv.Itoa(newDbId))
 	w.DbId = newDbId
+	w.chWaitReply <- &entry.Entry{
+		Argv:    []string{"select", strconv.Itoa(newDbId)},
+		CmdName: "select",
+	}
 }
 
 func (w *redisWriter) flushInterval() {
@@ -75,6 +80,9 @@ func (w *redisWriter) flushInterval() {
 				log.Panicf("redisWriter received error. error=[%v], argv=%v, slots=%v, reply=[%v]", err, e.Argv, e.Slots, reply)
 			}
 		}
+		if strings.EqualFold(e.CmdName, "select") { // skip select command
+			continue
+		}
 		atomic.AddUint64(&w.UpdateUnansweredBytesCount, ^(e.EncodedSize - 1))
 		statistics.UpdateAOFAppliedOffset(uint64(e.Offset))
 		statistics.UpdateUnansweredBytesCount(atomic.LoadUint64(&w.UpdateUnansweredBytesCount))