Fix bad range results on indexed fields

index/list_test.go

@@ -380,6 +380,30 @@ func TestListIndexRange(t *testing.T) {
 		require.Len(t, list, 2)
 		require.NoError(t, err)
 		assertEncodedIntListEqual(t, []int{5, 4}, list)
+
+		// issue #218
+		val, _ := gob.Codec.Marshal(8)
+		err = idx.Remove(val)
+		require.NoError(t, err)
+
+		// normal with gaps
+		min, _ = gob.Codec.Marshal(6)
+		max, _ = gob.Codec.Marshal(8)
+		list, err = idx.Range(min, max, nil)
+		require.Len(t, list, 2)
+		require.NoError(t, err)
+		assertEncodedIntListEqual(t, []int{6, 7}, list)
+
+		// reverse with gaps
+		min, _ = gob.Codec.Marshal(6)
+		max, _ = gob.Codec.Marshal(8)
+		opts = index.NewOptions()
+		opts.Reverse = true
+		list, err = idx.Range(min, max, opts)
+		require.Len(t, list, 2)
+		require.NoError(t, err)
+		assertEncodedIntListEqual(t, []int{7, 6}, list)
+
 		return nil
 	})
 }

internal/boltdb.go

@@ -42,7 +42,16 @@ type RangeCursor struct {
 // First element
 func (c *RangeCursor) First() ([]byte, []byte) {
 	if c.Reverse {
-		return c.C.Seek(c.Max)
+		k, v := c.C.Seek(c.Max)
+
+		// If Seek doesn't find a key it goes to the next.
+		// If so, we need to get the previous one to avoid
+		// including bigger values. #218
+		if !bytes.HasPrefix(k, c.Max) && k != nil {
+			k, v = c.C.Prev()
+		}
+
+		return k, v
 	}
 
 	return c.C.Seek(c.Min)