reorganize the NodeId to make the append works again and add a test

Author: irevoire

src/node_id.rs

@@ -9,9 +9,9 @@ use crate::ItemId;
 #[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[repr(u8)]
 pub enum NodeMode {
-    Item = 0,
+    Metadata = 0,
     Tree = 1,
-    Metadata = 2,
+    Item = 2,
 }
 
 impl TryFrom<u8> for NodeMode {

src/tests/binary_quantized.rs

@@ -47,8 +47,8 @@ fn write_and_retrieve_binary_quantized_vector() {
     insta::assert_snapshot!(handle, @r###"
     ==================
     Dumping index 0
-    Item 0: Leaf(Leaf { header: NodeHeaderBinaryQuantizedEuclidean { bias: 0.0 }, vector: [-1.0000, -1.0000, 1.0000, -1.0000, 1.0000, 1.0000, -1.0000, 1.0000, -1.0000, -1.0000, "other ..."] })
-    Tree 0: Descendants(Descendants { descendants: [0] })
     Root: Metadata { dimensions: 16, items: RoaringBitmap<[0]>, roots: [0], distance: "binary quantized euclidean" }
+    Tree 0: Descendants(Descendants { descendants: [0] })
+    Item 0: Leaf(Leaf { header: NodeHeaderBinaryQuantizedEuclidean { bias: 0.0 }, vector: [-1.0000, -1.0000, 1.0000, -1.0000, 1.0000, 1.0000, -1.0000, 1.0000, -1.0000, -1.0000, "other ..."] })
     "###);
 }

src/tests/reader.rs

@@ -112,10 +112,10 @@ fn two_dimension_on_a_line() {
     let reader = Reader::<Euclidean>::open(&rtxn, 0, handle.database).unwrap();
 
     // if we can't look into enough nodes we find some random points
-    let ret = reader.nns(5).search_k(NonZeroUsize::new(1).unwrap()).by_item(&rtxn, 0).unwrap();
+    let ret = reader.nns(5).search_k(NonZeroUsize::new(1).unwrap()).by_item(&rtxn, 1).unwrap();
     insta::assert_snapshot!(NnsRes(ret), @r###"
-    id(48): distance(48)
-    id(92): distance(92)
+    id(48): distance(47)
+    id(92): distance(91)
     "###);
 
     // if we can look into all the node there is no inifinite loop and it works
@@ -131,11 +131,11 @@ fn two_dimension_on_a_line() {
 
     let ret = reader.nns(5).by_item(&rtxn, 0).unwrap();
     insta::assert_snapshot!(NnsRes(ret), @r###"
+    id(0): distance(0)
     id(1): distance(1)
     id(2): distance(2)
     id(3): distance(3)
     id(4): distance(4)
-    id(5): distance(5)
     "###);
 }
 
@@ -162,11 +162,11 @@ fn two_dimension_on_a_column() {
     let ret = reader.nns(5).by_item(&rtxn, 0).unwrap();
 
     insta::assert_snapshot!(NnsRes(ret), @r###"
+    id(0): distance(0)
     id(1): distance(1)
     id(2): distance(2)
     id(3): distance(3)
     id(4): distance(4)
-    id(5): distance(5)
     "###);
 }
 

src/tests/snapshots/arroy__tests__writer__write_and_update_lot_of_random_points-2.snap

@@ -265,6 +265,7 @@ impl<D: Distance> Writer<D> {
             .remap_data_type::<RoaringBitmapCodec>()
             .get(wtxn, &Key::updated(self.index))?
             .unwrap_or_default();
+        // We cannot append here because we may have removed an item with a larger id before
         updated.insert(item);
         self.database.remap_data_type::<RoaringBitmapCodec>().put(
             wtxn,