boltdb loop cursor

bolt_loop.go

package main

import (
	"fmt"
	"log"
	"sort"
	"strconv"

	"github.com/boltdb/bolt"
)

func byteToInt(b []byte) int {
	byteToInt, _ := strconv.Atoi(string(b))
	return byteToInt
}

func intToByte(b int) []byte {
	pk := strconv.Itoa(b)
	return []byte(pk)
}

const MaxLen = 5

func main() {
	db, err := bolt.Open("my.db", 0600, nil)
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	//for i := 0; i < 10; i++ {
	//	db.Update(func(tx *bolt.Tx) error {
	//		b, _ := tx.CreateBucketIfNotExists([]byte("MyBucket"))
	//		id, _ := b.NextSequence()
	//		return b.Put(intToByte(int(id)), intToByte(int(id)))
	//	})
	//}

	db.Update(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte("MyBucket"))
		c := b.Cursor()
		var ids []int
		for k, _ := c.First(); k != nil; k, _ = c.Next() {
			//fmt.Printf("current key=%s, value=%s\n", k, v)
			ids = append(ids, byteToInt(k))
		}
		if len(ids) > MaxLen {
			sort.Ints(ids)
			ids = ids[:len(ids)-MaxLen]
			for _, v := range ids {
				if err := b.Delete(intToByte(v)); err != nil {
					panic(err)
				}
				//fmt.Println("delete ", intToByte(v))
			}
		}
		id, _ := b.NextSequence()
		return b.Put(intToByte(int(id)), intToByte(int(id)))
	})

	db.View(func(tx *bolt.Tx) error {
		b := tx.Bucket([]byte("MyBucket"))
		c := b.Cursor()
		for k, v := c.Last(); k != nil; k, v = c.Prev() {
			fmt.Printf("current key=%s, value=%s\n", k, v)

		}
		return nil
	})
}