Add support for Range Scan

bitcask.go

@@ -1,6 +1,7 @@
 package bitcask
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"hash/crc32"
@@ -270,6 +271,24 @@ func (b *Bitcask) Scan(prefix []byte, f func(key []byte) error) (err error) {
 	return
 }
 
+// Range performs a range scan of keys matching a range of keys between the
+// start key and end key 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) Range(start, end []byte, f func(key []byte) error) (err error) {
+	b.trie.ForEach(func(node art.Node) bool {
+		if bytes.Compare(node.Key(), start) >= 0 && bytes.Compare(node.Key(), end) <= 0 {
+			if err = f(node.Key()); err != nil {
+				return false
+			}
+			return true
+		} else {
+			return false
+		}
+	})
+	return
+}
+
 // Len returns the total number of keys in the database
 func (b *Bitcask) Len() int {
 	b.mu.RLock()

bitcask_test.go

@@ -1626,6 +1626,61 @@ func TestScan(t *testing.T) {
 	})
 }
 
+func TestRange(t *testing.T) {
+	assert := assert.New(t)
+
+	testdir, err := ioutil.TempDir("", "bitcask")
+	assert.NoError(err)
+
+	var db *Bitcask
+
+	t.Run("Setup", func(t *testing.T) {
+		t.Run("Open", func(t *testing.T) {
+			db, err = Open(testdir)
+			assert.NoError(err)
+		})
+
+		t.Run("Put", func(t *testing.T) {
+			for i := 1; i < 10; i++ {
+				key := []byte(fmt.Sprintf("foo_%d", i))
+				val := []byte(fmt.Sprintf("%d", i))
+				err = db.Put(key, val)
+				assert.NoError(err)
+			}
+		})
+	})
+
+	t.Run("Range", func(t *testing.T) {
+		var (
+			vals     [][]byte
+			expected = [][]byte{
+				[]byte("3"),
+				[]byte("4"),
+				[]byte("5"),
+				[]byte("6"),
+				[]byte("7"),
+			}
+		)
+
+		err = db.Range([]byte("foo_3"), []byte("foo_7"), func(key []byte) error {
+			val, err := db.Get(key)
+			assert.NoError(err)
+			vals = append(vals, val)
+			return nil
+		})
+		vals = SortByteArrays(vals)
+		assert.Equal(expected, vals)
+	})
+
+	t.Run("RangeErrors", func(t *testing.T) {
+		err = db.Range([]byte("foo_3"), []byte("foo_7"), func(key []byte) error {
+			return ErrMockError
+		})
+		assert.Error(err)
+		assert.Equal(ErrMockError, err)
+	})
+}
+
 func TestLocking(t *testing.T) {
 	assert := assert.New(t)
 

cmd/bitcask/range.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
+
+	"github.com/prologic/bitcask"
+)
+
+var rangeCmd = &cobra.Command{
+	Use:     "range <start> <end>",
+	Aliases: []string{},
+	Short:   "Perform a range scan for keys from a start to end key",
+	Long: `This performa a range scan for keys  starting with the given start
+key and ending with the end key. This uses a Trie to search for matching keys
+within the range and returns all matched keys.`,
+	Args: cobra.ExactArgs(2),
+	Run: func(cmd *cobra.Command, args []string) {
+		path := viper.GetString("path")
+
+		start := args[0]
+		end := args[1]
+
+		os.Exit(_range(path, start, end))
+	},
+}
+
+func init() {
+	RootCmd.AddCommand(rangeCmd)
+}
+
+func _range(path, start, end string) int {
+	db, err := bitcask.Open(path)
+	if err != nil {
+		log.WithError(err).Error("error opening database")
+		return 1
+	}
+	defer db.Close()
+
+	err = db.Range([]byte(start), []byte(end), func(key []byte) error {
+		value, err := db.Get(key)
+		if err != nil {
+			log.WithError(err).Error("error reading key")
+			return err
+		}
+
+		fmt.Printf("%s\n", string(value))
+		log.WithField("key", key).WithField("value", value).Debug("key/value")
+		return nil
+	})
+	if err != nil {
+		log.WithError(err).Error("error rangening keys")
+		return 1
+	}
+
+	return 0
+}