Fix successor with empty keys

internal/database/pebble/open.go

@@ -1,8 +1,6 @@
 package pebble
 
 import (
-	"fmt"
-
 	"github.com/cockroachdb/pebble"
 	"github.com/genjidb/genji/internal/encoding"
 )
@@ -31,45 +29,3 @@ var DefaultComparer = &pebble.Comparer{
 	// format, and should not be changed.
 	Name: "leveldb.BytewiseComparator",
 }
-
-var stats = struct {
-	SuccessorCount int
-	SeparatorCount int
-	CompareCount   int
-	EqualCount     int
-	AbbrevCount    int
-	FormatKeyCount int
-}{}
-
-// DefaultComparer is the default implementation of the Comparer interface for Genji.
-func WithStats(cmp *pebble.Comparer) *pebble.Comparer {
-	return &pebble.Comparer{
-		Compare: func(a, b []byte) int {
-			stats.CompareCount++
-			return cmp.Compare(a, b)
-		},
-		Equal: func(a, b []byte) bool {
-			stats.EqualCount++
-			return cmp.Equal(a, b)
-		},
-		AbbreviatedKey: func(key []byte) uint64 {
-			stats.AbbrevCount++
-			return cmp.AbbreviatedKey(key)
-		},
-		FormatKey: func(key []byte) fmt.Formatter {
-			stats.FormatKeyCount++
-			return cmp.FormatKey(key)
-		},
-		Separator: func(dst, a, b []byte) []byte {
-			stats.SeparatorCount++
-			return cmp.Separator(dst, a, b)
-		},
-		Successor: func(dst, a []byte) []byte {
-			stats.SuccessorCount++
-			return cmp.Successor(dst, a)
-		},
-		// This name is part of the C++ Level-DB implementation's default file
-		// format, and should not be changed.
-		Name: "leveldb.BytewiseComparator",
-	}
-}

internal/database/pebble/open_test.go

@@ -79,7 +79,7 @@ func TestPebbleBatchSet(t *testing.T) {
 	var opts pebble.Options
 	opts.FS = vfs.NewMem()
 
-	opts.Comparer = WithStats(DefaultComparer)
+	opts.Comparer = DefaultComparer
 
 	db, err := Open("", &opts)
 	require.NoError(t, err)

internal/encoding/helpers.go

@@ -240,6 +240,10 @@ func compareNextValue(a, b []byte) (cmp int, n int) {
 }
 
 func Successor(dst, a []byte) []byte {
+	if len(a) == 0 {
+		return a
+	}
+
 	namespace, _ := DecodeInt(a)
 	if namespace == math.MaxInt64 {
 		return a