Use custom Separator function

internal/database/pebble/open.go

@@ -23,7 +23,7 @@ var DefaultComparer = &pebble.Comparer{
 	Equal:          encoding.Equal,
 	AbbreviatedKey: encoding.AbbreviatedKey,
 	FormatKey:      pebble.DefaultComparer.FormatKey,
-	Separator:      pebble.DefaultComparer.Separator,
+	Separator:      encoding.Separator,
 	Successor:      encoding.Successor,
 	// This name is part of the C++ Level-DB implementation's default file
 	// format, and should not be changed.

internal/encoding/helpers.go

@@ -353,5 +353,28 @@ func abbreviatedValue(key []byte) uint64 {
 	}
 
 	return 0
-	// panic(fmt.Sprintf("unsupported value type: %d, %v", key[0], key))
+}
+
+func Separator(dst, a, b []byte) (foo []byte) {
+	var n, cmp int
+	var idx int
+	var aa []byte = a
+
+	for {
+		if n == len(a) {
+			return a
+		}
+
+		a = a[n:]
+		b = b[n:]
+		idx += n
+
+		cmp, n = compareNextValue(a, b)
+		if cmp != 0 {
+			idx += n
+			dst = append(dst, aa[:idx]...)
+			dst = append(dst, 0xFF)
+			return dst
+		}
+	}
 }

internal/encoding/helpers_test.go

@@ -243,3 +243,26 @@ func TestAbbreviatedKey(t *testing.T) {
 		})
 	}
 }
+
+func TestSeparator(t *testing.T) {
+	tests := []struct {
+		k1, k2 string
+	}{
+		{`[1, 1]`, `[1, 2]`},
+		{`[1, 1]`, `[1, 3]`},
+	}
+
+	for _, test := range tests {
+		t.Run(fmt.Sprintf("Separator(%v, %v)", test.k1, test.k2), func(t *testing.T) {
+			v1, err := testutil.ParseExpr(t, test.k1).Eval(&environment.Environment{})
+			require.NoError(t, err)
+			v2, err := testutil.ParseExpr(t, test.k2).Eval(&environment.Environment{})
+			require.NoError(t, err)
+			k1 := mustNewKey(t, v1.V().(*document.ValueBuffer).Values...)
+			k2 := mustNewKey(t, v2.V().(*document.ValueBuffer).Values...)
+			sep := encoding.Separator(nil, k1, k2)
+			require.LessOrEqual(t, encoding.Compare(k1, sep), 0)
+			require.Less(t, encoding.Compare(sep, k2), 0)
+		})
+	}
+}