Replace keydir with ART trie (#75)

* Replace keydir with ART trie

* Address some review feedback

* Address review feedback (consts)

bitcask.go

@@ -1,7 +1,6 @@
 package bitcask
 
 import (
-	"bytes"
 	"encoding/json"
 	"errors"
 	"hash/crc32"
@@ -13,8 +12,7 @@ import (
 	"sync"
 
 	"github.com/gofrs/flock"
-	"github.com/plar/go-adaptive-radix-tree"
-
+	art "github.com/plar/go-adaptive-radix-tree"
 	"github.com/prologic/bitcask/internal"
 )
 
@@ -51,7 +49,6 @@ type Bitcask struct {
 	options   []Option
 	path      string
 	curr      *internal.Datafile
-	keydir    *internal.Keydir
 	datafiles map[int]*internal.Datafile
 	trie      art.Tree
 }
@@ -74,7 +71,9 @@ func (b *Bitcask) Stats() (stats Stats, err error) {
 	}
 
 	stats.Datafiles = len(b.datafiles)
-	stats.Keys = b.keydir.Len()
+	b.mu.RLock()
+	stats.Keys = b.trie.Size()
+	b.mu.RUnlock()
 	stats.Size = size
 
 	return
@@ -89,7 +88,16 @@ func (b *Bitcask) Close() error {
 		os.Remove(b.Flock.Path())
 	}()
 
-	if err := b.keydir.Save(path.Join(b.path, "index")); err != nil {
+	f, err := os.OpenFile(filepath.Join(b.path, "index"), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	if err := internal.WriteIndex(b.trie, f); err != nil {
+		return err
+	}
+	if err := f.Sync(); err != nil {
 		return err
 	}
 
@@ -112,11 +120,15 @@ func (b *Bitcask) Sync() error {
 func (b *Bitcask) Get(key []byte) ([]byte, error) {
 	var df *internal.Datafile
 
-	item, ok := b.keydir.Get(key)
-	if !ok {
+	b.mu.RLock()
+	value, found := b.trie.Search(key)
+	b.mu.RUnlock()
+	if !found {
 		return nil, ErrKeyNotFound
 	}
 
+	item := value.(internal.Item)
+
 	if item.FileID == b.curr.FileID() {
 		df = b.curr
 	} else {
@@ -138,8 +150,10 @@ func (b *Bitcask) Get(key []byte) ([]byte, error) {
 
 // Has returns true if the key exists in the database, false otherwise.
 func (b *Bitcask) Has(key []byte) bool {
-	_, ok := b.keydir.Get(key)
-	return ok
+	b.mu.RLock()
+	_, found := b.trie.Search(key)
+	b.mu.RUnlock()
+	return found
 }
 
 // Put stores the key and value in the database.
@@ -162,11 +176,10 @@ func (b *Bitcask) Put(key, value []byte) error {
 		}
 	}
 
-	item := b.keydir.Add(key, b.curr.FileID(), offset, n)
-
-	if b.config.greedyScan {
+	item := internal.Item{b.curr.FileID(), offset, n}
+	b.mu.Lock()
 	b.trie.Insert(key, item)
-	}
+	b.mu.Unlock()
 
 	return nil
 }
@@ -179,11 +192,9 @@ func (b *Bitcask) Delete(key []byte) error {
 		return err
 	}
 
-	b.keydir.Delete(key)
-
-	if b.config.greedyScan {
+	b.mu.Lock()
 	b.trie.Delete(key)
-	}
+	b.mu.Unlock()
 
 	return nil
 }
@@ -191,48 +202,65 @@ func (b *Bitcask) Delete(key []byte) error {
 // Scan performs a prefix scan of keys matching the given prefix and calling
 // the function `f` with the keys found. If the function returns an error
 // no further keys are processed and the first error returned.
-func (b *Bitcask) Scan(prefix []byte, f func(key []byte) error) error {
-	if b.config.greedyScan {
+func (b *Bitcask) Scan(prefix []byte, f func(key []byte) error) (err error) {
 	b.trie.ForEachPrefix(prefix, func(node art.Node) bool {
-			if err := f(node.Key()); err != nil {
+		// Skip the root node
+		if len(node.Key()) == 0 {
+			return true
+		}
+
+		if err = f(node.Key()); err != nil {
 			return false
 		}
 		return true
 	})
-		return nil
-	}
-
-	keys := b.Keys()
-	for key := range keys {
-		if bytes.Equal(prefix, key[:len(prefix)]) {
-			if err := f([]byte(key)); err != nil {
-				return err
-			}
-		}
-	}
-
-	return nil
+	return
 }
 
 // Len returns the total number of keys in the database
 func (b *Bitcask) Len() int {
-	return b.keydir.Len()
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+	return b.trie.Size()
 }
 
-// Keys returns all keys in the database as a channel of string(s)
+// Keys returns all keys in the database as a channel of keys
 func (b *Bitcask) Keys() chan []byte {
-	return b.keydir.Keys()
+	ch := make(chan []byte)
+	go func() {
+		b.mu.RLock()
+		defer b.mu.RUnlock()
+
+		for it := b.trie.Iterator(); it.HasNext(); {
+			node, _ := it.Next()
+
+			// Skip the root node
+			if len(node.Key()) == 0 {
+				continue
+			}
+
+			ch <- node.Key()
+		}
+		close(ch)
+	}()
+
+	return ch
 }
 
 // Fold iterates over all keys in the database calling the function `f` for
 // each key. If the function returns an error, no further keys are processed
 // and the error returned.
 func (b *Bitcask) Fold(f func(key []byte) error) error {
-	for key := range b.keydir.Keys() {
-		if err := f(key); err != nil {
-			return err
-		}
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+
+	b.trie.ForEach(func(node art.Node) bool {
+		if err := f(node.Key()); err != nil {
+			return false
 		}
+		return true
+	})
+
 	return nil
 }
 
@@ -314,22 +342,17 @@ func (b *Bitcask) reopen() error {
 		datafiles[id] = df
 	}
 
-	keydir := internal.NewKeydir()
-
-	var t art.Tree
-	if b.config.greedyScan {
-		t = art.New()
-	}
+	t := art.New()
 
 	if internal.Exists(path.Join(b.path, "index")) {
-		if err := keydir.Load(path.Join(b.path, "index")); err != nil {
+		f, err := os.Open(path.Join(b.path, "index"))
+		if err != nil {
 			return err
 		}
-		for key := range keydir.Keys() {
-			item, _ := keydir.Get(key)
-			if b.config.greedyScan {
-				t.Insert(key, item)
-			}
+		defer f.Close()
+
+		if err := internal.ReadIndex(f, t); err != nil {
+			return err
 		}
 	} else {
 		for i, df := range datafiles {
@@ -344,17 +367,15 @@ func (b *Bitcask) reopen() error {
 
 				// Tombstone value  (deleted key)
 				if len(e.Value) == 0 {
-					keydir.Delete(e.Key)
+					t.Delete(e.Key)
 					continue
 				}
 
-				item := keydir.Add(e.Key, ids[i], e.Offset, n)
-				if b.config.greedyScan {
+				item := internal.Item{ids[i], e.Offset, n}
 				t.Insert(e.Key, item)
 			}
 		}
 	}
-	}
 
 	var id int
 	if len(ids) > 0 {
@@ -366,15 +387,10 @@ func (b *Bitcask) reopen() error {
 		return err
 	}
 
+	b.trie = t
 	b.curr = curr
 	b.datafiles = datafiles
 
-	b.keydir = keydir
-
-	if b.config.greedyScan {
-		b.trie = t
-	}
-
 	return nil
 }
 

go.mod

@@ -3,7 +3,6 @@ module github.com/prologic/bitcask
 go 1.12
 
 require (
-	github.com/derekparker/trie v0.0.0-20190805173922-4e1a77fb815d
 	github.com/gofrs/flock v0.7.1
 	github.com/konsorten/go-windows-terminal-sequences v1.0.2 // indirect
 	github.com/magiconair/properties v1.8.1 // indirect

go.sum

@@ -20,8 +20,6 @@ github.com/cpuguy83/go-md2man v1.0.10/go.mod h1:SmD6nW6nTyfqj6ABTjUi3V3JVMnlJmwc
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/derekparker/trie v0.0.0-20190805173922-4e1a77fb815d h1:TocZO8frNoxkwqFPePHFldSw8vLu+gBrlvFZYWqxiF4=
-github.com/derekparker/trie v0.0.0-20190805173922-4e1a77fb815d/go.mod h1:D6ICZm05D9VN1n/8iOtBxLpXtoGp6HDFUJ1RNVieOSE=
 github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
 github.com/dgryski/go-sip13 v0.0.0-20181026042036-e10d5fee7954/go.mod h1:vAd38F8PWV+bWy6jNmig1y/TA+kYO4g3RSRF0IAv0no=
 github.com/fsnotify/fsnotify v1.4.7 h1:IXs+QLmnXW2CcXuY+8Mzv/fWEsPGWxqefPtCP5CnV9I=

internal/codec_index.go

@@ -0,0 +1,110 @@
+package internal
+
+import (
+	"encoding/binary"
+	"io"
+
+	art "github.com/plar/go-adaptive-radix-tree"
+)
+
+const (
+	Int32Size  = 4
+	Int64Size  = 8
+	FileIDSize = Int32Size
+	OffsetSize = Int64Size
+	SizeSize   = Int64Size
+)
+
+func ReadBytes(r io.Reader) ([]byte, error) {
+	s := make([]byte, Int32Size)
+	_, err := io.ReadFull(r, s)
+	if err != nil {
+		return nil, err
+	}
+	size := binary.BigEndian.Uint32(s)
+	b := make([]byte, size)
+	_, err = io.ReadFull(r, b)
+	if err != nil {
+		return nil, err
+	}
+	return b, nil
+}
+
+func WriteBytes(b []byte, w io.Writer) (int, error) {
+	s := make([]byte, Int32Size)
+	binary.BigEndian.PutUint32(s, uint32(len(b)))
+	n, err := w.Write(s)
+	if err != nil {
+		return n, err
+	}
+	m, err := w.Write(b)
+	if err != nil {
+		return (n + m), err
+	}
+	return (n + m), nil
+}
+
+func ReadItem(r io.Reader) (Item, error) {
+	buf := make([]byte, (FileIDSize + OffsetSize + SizeSize))
+	_, err := io.ReadFull(r, buf)
+	if err != nil {
+		return Item{}, err
+	}
+
+	return Item{
+		FileID: int(binary.BigEndian.Uint32(buf[:FileIDSize])),
+		Offset: int64(binary.BigEndian.Uint64(buf[FileIDSize:(FileIDSize + OffsetSize)])),
+		Size:   int64(binary.BigEndian.Uint64(buf[(FileIDSize + OffsetSize):])),
+	}, nil
+}
+
+func WriteItem(item Item, w io.Writer) (int, error) {
+	buf := make([]byte, (FileIDSize + OffsetSize + SizeSize))
+	binary.BigEndian.PutUint32(buf[:FileIDSize], uint32(item.FileID))
+	binary.BigEndian.PutUint64(buf[FileIDSize:(FileIDSize+OffsetSize)], uint64(item.Offset))
+	binary.BigEndian.PutUint64(buf[(FileIDSize+OffsetSize):], uint64(item.Size))
+	n, err := w.Write(buf)
+	if err != nil {
+		return 0, err
+	}
+	return n, nil
+}
+
+func ReadIndex(r io.Reader, t art.Tree) error {
+	for {
+		key, err := ReadBytes(r)
+		if err != nil {
+			if err == io.EOF {
+				break
+			}
+			return err
+		}
+
+		item, err := ReadItem(r)
+		if err != nil {
+			return err
+		}
+
+		t.Insert(key, item)
+	}
+
+	return nil
+}
+
+func WriteIndex(t art.Tree, w io.Writer) (err error) {
+	t.ForEach(func(node art.Node) bool {
+		_, err = WriteBytes(node.Key(), w)
+		if err != nil {
+			return false
+		}
+
+		item := node.Value().(Item)
+		_, err := WriteItem(item, w)
+		if err != nil {
+			return false
+		}
+
+		return true
+	})
+	return
+}

internal/item.go

@@ -0,0 +1,7 @@
+package internal
+
+type Item struct {
+	FileID int   `json:"fileid"`
+	Offset int64 `json:"offset"`
+	Size   int64 `json:"size"`
+}

internal/keydir.go

@@ -1,129 +0,0 @@
-package internal
-
-import (
-	"bytes"
-	"encoding/gob"
-	"io"
-	"io/ioutil"
-	"os"
-	"sync"
-)
-
-type Item struct {
-	FileID int
-	Offset int64
-	Size   int64
-}
-
-type Keydir struct {
-	sync.RWMutex
-	keys  map[uint64][]byte
-	items map[uint64]Item
-}
-
-func NewKeydir() *Keydir {
-	return &Keydir{
-		keys:  make(map[uint64][]byte),
-		items: make(map[uint64]Item),
-	}
-}
-
-func (k *Keydir) Add(key []byte, fileid int, offset, size int64) Item {
-	item := Item{
-		FileID: fileid,
-		Offset: offset,
-		Size:   size,
-	}
-
-	hash := Hash(key)
-
-	k.Lock()
-	k.keys[hash] = key
-	k.items[hash] = item
-	k.Unlock()
-
-	return item
-}
-
-func (k *Keydir) Get(key []byte) (Item, bool) {
-	k.RLock()
-	item, ok := k.items[Hash(key)]
-	k.RUnlock()
-	return item, ok
-}
-
-func (k *Keydir) Delete(key []byte) {
-	hash := Hash(key)
-	k.Lock()
-	delete(k.keys, hash)
-	delete(k.items, hash)
-	k.Unlock()
-}
-
-func (k *Keydir) Len() int {
-	return len(k.keys)
-}
-
-func (k *Keydir) Keys() chan []byte {
-	ch := make(chan []byte)
-	go func() {
-		k.RLock()
-		for _, key := range k.keys {
-			ch <- key
-		}
-		close(ch)
-		k.RUnlock()
-	}()
-	return ch
-}
-
-func (k *Keydir) Bytes() ([]byte, error) {
-	var buf bytes.Buffer
-	enc := gob.NewEncoder(&buf)
-	if err := enc.Encode(k.keys); err != nil {
-		return nil, err
-	}
-	if err := enc.Encode(k.items); err != nil {
-		return nil, err
-	}
-	return buf.Bytes(), nil
-}
-
-func (k *Keydir) Load(fn string) error {
-	f, err := os.Open(fn)
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-
-	dec := gob.NewDecoder(f)
-	if err := dec.Decode(&k.keys); err != nil {
-		return err
-	}
-	if err := dec.Decode(&k.items); err != nil {
-		return err
-	}
-
-	return nil
-}
-
-func (k *Keydir) Save(fn string) error {
-	data, err := k.Bytes()
-	if err != nil {
-		return err
-	}
-
-	return ioutil.WriteFile(fn, data, 0644)
-}
-
-func NewKeydirFromBytes(r io.Reader) (*Keydir, error) {
-	k := NewKeydir()
-	dec := gob.NewDecoder(r)
-	if err := dec.Decode(&k.keys); err != nil {
-		return nil, err
-	}
-	if err := dec.Decode(&k.items); err != nil {
-		return nil, err
-	}
-	return k, nil
-}

internal/utils.go

@@ -9,20 +9,6 @@ import (
 	"strings"
 )
 
-const (
-	offset64 = 14695981039346656037
-	prime64  = 1099511628211
-)
-
-func Hash(key []byte) uint64 {
-	var s uint64 = offset64
-	for _, c := range key {
-		s ^= uint64(c)
-		s *= prime64
-	}
-	return s
-}
-
 func Exists(path string) bool {
 	_, err := os.Stat(path)
 	return err == nil

options.go

@@ -25,7 +25,6 @@ type config struct {
 	maxKeySize      int
 	maxValueSize    int
 	sync            bool
-	greedyScan      bool
 }
 
 func (c *config) MarshalJSON() ([]byte, error) {
@@ -34,13 +33,11 @@ func (c *config) MarshalJSON() ([]byte, error) {
 		MaxKeySize      int  `json:"max_key_size"`
 		MaxValueSize    int  `json:"max_value_size"`
 		Sync            bool `json:"sync"`
-		GreedyScan      bool `json:"greedy_scan"`
 	}{
 		MaxDatafileSize: c.maxDatafileSize,
 		MaxKeySize:      c.maxKeySize,
 		MaxValueSize:    c.maxValueSize,
 		Sync:            c.sync,
-		GreedyScan:      c.greedyScan,
 	})
 }
 
@@ -50,7 +47,6 @@ func getConfig(path string) (*config, error) {
 		MaxKeySize      int  `json:"max_key_size"`
 		MaxValueSize    int  `json:"max_value_size"`
 		Sync            bool `json:"sync"`
-		GreedyScan      bool `json:"greedy_scan"`
 	}
 
 	var cfg Config
@@ -69,7 +65,6 @@ func getConfig(path string) (*config, error) {
 		maxKeySize:      cfg.MaxKeySize,
 		maxValueSize:    cfg.MaxValueSize,
 		sync:            cfg.Sync,
-		greedyScan:      cfg.GreedyScan,
 	}, nil
 }
 
@@ -113,12 +108,3 @@ func WithSync(sync bool) Option {
 		return nil
 	}
 }
-
-// WithGreedyScan enables faster Scan performance.
-// This is disabled by default because it causes high memory usage.
-func WithGreedyScan(enabled bool) Option {
-	return func(cfg *config) error {
-		cfg.greedyScan = enabled
-		return nil
-	}
-}