reviter.go

// test about the reverse iter
package main

import (
	"context"
	"flag"
	"log"
	"strings"

	"github.com/pingcap/tidb/kv"
	"github.com/pingcap/tidb/store/mockstore"
	"github.com/pingcap/tidb/store/tikv"
)

// KV pairs
type KV struct {
	Key   string
	Value string
}

// PutKeyValues write the key values into database
func PutKeyValues(s kv.Storage) {
	txn, err := s.Begin()
	if err != nil {
		log.Fatal(err)
	}
	kvs := []*KV{
		{"aaa", "1"},
		{"bbb", "2"},
		{"ccc", "3"},
		{"ddd", "4"},
		{"eee", "5"},
		{"fff", "6"},
	}
	for _, kv := range kvs {
		txn.Set([]byte(kv.Key), []byte(kv.Value))
	}

	if err := txn.Commit(context.Background()); err != nil {
		log.Fatal(err)
	}
}

// Reviter iterates the key values in the reverse order
func Reviter(s kv.Storage) {
	txn, err := s.Begin()
	if err != nil {
		log.Fatal(err)
	}
	iter, err := txn.IterReverse([]byte("eee"))
	if err != nil {
		log.Fatal(err)
	}
	for iter.Valid() {
		log.Println(string(iter.Key()), string(iter.Value()))
		iter.Next()
	}
	txn.Commit(context.Background())
}

func main() {
	var addr string
	flag.StringVar(&addr, "addr", "tikv://127.0.0.1:2379", "tikv cluster address")
	flag.Parse()

	var store kv.Storage
	var err error

	open := tikv.Driver{}.Open
	if strings.HasPrefix(addr, "mocktikv://") {
		open = mockstore.MockDriver{}.Open
	}
	store, err = open(addr)
	if err != nil {
		log.Fatal(err)
	}
	PutKeyValues(store)
	Reviter(store)
}