feat(key-revision): add revision for keys with GetUsingRevision function

Makefile

@@ -8,7 +8,8 @@ build:
 	go build -v
 
 clean:
-	rm -rf ./nimbusdb_temp* benchmark/nimbusdb_temp*
+	rm -rf ./nimbusdb_temp* benchmark/nimbusdb_temp* ~/nimbusdb/test_data
+	mkdir -p ~/nimbusdb/test_data
 
 test:
 	go test -v -failfast

batch.go

@@ -3,7 +3,6 @@ package nimbusdb
 import (
 	"bytes"
 	"errors"
-	"sync"
 	"time"
 
 	"github.com/manosriram/nimbusdb/utils"
@@ -15,15 +14,6 @@ var (
 	ERROR_CANNOT_CLOSE_CLOSED_BATCH = errors.New("cannot close closed batch")
 )
 
-type Batch struct {
-	id         ksuid.KSUID
-	db         *Db
-	closed     bool
-	batchlock  sync.Mutex
-	mu         sync.RWMutex
-	writeQueue []*KeyValuePair
-}
-
 func (db *Db) NewBatch() (*Batch, error) {
 	b := &Batch{
 		db:     db,
@@ -73,11 +63,11 @@ func (b *Batch) Get(k []byte) ([]byte, error) {
 		return utils.Encode(record.Value), nil
 	}
 
-	v, err := b.db.getKeyDir(k) // else, search datafiles
+	v, err := b.db.getKeyDirUsingKey(k) // else, search datafiles
 	if err != nil {
 		return nil, err
 	}
-	return v.v, nil
+	return v.value, nil
 }
 
 func (b *Batch) Exists(k []byte) (bool, error) {
@@ -98,11 +88,11 @@ func (b *Batch) Exists(k []byte) (bool, error) {
 		return true, nil
 	}
 
-	v, err := b.db.getKeyDir(k) // else, search datafiles
+	v, err := b.db.getKeyDirUsingKey(k) // else, search datafiles
 	if err != nil {
 		return false, err
 	}
-	return bytes.Equal(v.k, k), nil
+	return bytes.Equal(v.key, k), nil
 }
 
 func (b *Batch) Set(k []byte, v []byte) ([]byte, error) {

btree.go

@@ -2,6 +2,7 @@ package nimbusdb
 
 import (
 	"bytes"
+	"strings"
 	"sync"
 
 	"github.com/google/btree"
@@ -14,24 +15,46 @@ type BTree struct {
 }
 
 type item struct {
-	key []byte
-	v   KeyDirValue
+	key      []byte
+	v        KeyDirValue
+	revision int64
 }
 
-func (it item) Less(i btree.Item) bool {
-	return bytes.Compare(it.key, i.(*item).key) < 0
+func (i item) Less(other btree.Item) bool {
+	otherItem := other.(*item)
+
+	if bytes.Equal(i.key, otherItem.key) {
+		switch i.revision {
+		case 0:
+			return i.revision > otherItem.revision
+		default:
+			return i.revision < otherItem.revision
+		}
+	}
+	return bytes.Compare(i.key, otherItem.key) < 0
+
 }
 
 func (b *BTree) Get(key []byte) *KeyDirValue {
 	i := b.tree.Get(&item{key: key})
 	if i == nil {
 		return nil
 	}
-	return &i.(*item).v
+	v := &i.(*item).v
+	return v
+}
+
+func (b *BTree) GetUsingRevision(key []byte, revision int64) *KeyDirValue {
+	i := b.tree.Get(&item{key: key, revision: revision})
+	if i == nil {
+		return nil
+	}
+	v := &i.(*item).v
+	return v
 }
 
 func (b *BTree) Set(key []byte, value KeyDirValue) *KeyDirValue {
-	i := b.tree.ReplaceOrInsert(&item{key: key, v: value})
+	i := b.tree.ReplaceOrInsert(&item{key: key, v: value, revision: value.revision})
 	if i != nil {
 		return &i.(*item).v
 	}
@@ -63,3 +86,13 @@ func (b *BTree) List() []*KeyValuePair {
 	})
 	return pairs
 }
+
+func (b *BTree) AscendWithPrefix(prefix string, handler func(k []byte)) {
+	b.tree.Ascend(func(it btree.Item) bool {
+		key := it.(*item).key
+		if strings.HasPrefix(string(key), prefix) {
+			handler(key)
+		}
+		return true
+	})
+}