badgerdb sequences

sequences.go

package main

import (
	"encoding/binary"
	"fmt"
	"sync"
	"sync/atomic"

	"github.com/dgraph-io/badger/v4"
)

const parallelism = 10

// can you use reverse iterators to create a "sequence"?
func main() {
	opts := badger.DefaultOptions("/tmp/badger")
	opts.Logger = nil
	db, err := badger.Open(opts)
	if err != nil {
		panic(err)
	}
	defer db.Close()

	if err := db.DropAll(); err != nil {
		panic(err)
	}

	iteratorOps := badger.DefaultIteratorOptions
	iteratorOps.PrefetchValues = false
	iteratorOps.Reverse = true

	var wg sync.WaitGroup

	// badgerdb attempt
	for i := 0; i < parallelism; i++ {
		wg.Add(1)
		go func() {
			txn := db.NewTransaction(true)
			defer txn.Discard()
			var idx uint64
			func() {
				it := txn.NewIterator(iteratorOps)
				defer it.Close()
				it.Rewind()
				if it.Valid() {
					k := it.Item().Key()
					idx := binary.BigEndian.Uint64(k)
					idx++
				}
			}()

			byteSlice := make([]byte, 8)
			binary.BigEndian.PutUint64(byteSlice, idx)
			if err := txn.Set(byteSlice, []byte("0")); err != nil {
				panic(err)
			}
			if err := txn.Commit(); err != nil {
				panic(err)
			}
			wg.Done()
		}()
	}
	wg.Wait()

	func() {
		txn := db.NewTransaction(false)
		it := txn.NewIterator(iteratorOps)
		it.Rewind()
		defer it.Close()
		var k []byte
		defer it.Close()
		for it.Valid() {
			k = it.Item().Key()
			fmt.Println("badgerdb", len(k), binary.BigEndian.Uint64(k))
			it.Next()
		}
		txn.Commit()
	}()

	if err := db.DropAll(); err != nil {
		panic(err)
	}

	// sync/atomic attempt
	var op atomic.Uint64
	op.Store(5)
	for i := 0; i < parallelism; i++ {
		wg.Add(1)
		go func() {
			txn := db.NewTransaction(true)
			defer txn.Discard()

			byteSlice := make([]byte, 8)
			binary.BigEndian.PutUint64(byteSlice, op.Add(1))
			if err := txn.Set(byteSlice, []byte("0")); err != nil {
				panic(err)
			}
			if err := txn.Commit(); err != nil {
				panic(err)
			}
			wg.Done()
		}()
	}
	wg.Wait()
	func() {
		var k []byte
		txn := db.NewTransaction(false)
		defer txn.Discard()
		it := txn.NewIterator(iteratorOps)
		it.Rewind()
		defer it.Close()
		for it.Valid() {
			k = it.Item().Key()
			fmt.Println("atomic", k, binary.BigEndian.Uint64(k))
			it.Next()
		}
		txn.Commit()
	}()
}