Add a method on reader to get all the item ids

Author: irevoire

src/reader.rs

@@ -71,6 +71,11 @@ impl<'t, D: Distance> Reader<'t, D> {
         self.items.len()
     }
 
+    /// Returns all the item ids contained in this index.
+    pub fn item_ids(&self) -> &RoaringBitmap {
+        &self.items
+    }
+
     /// Returns the index of this reader in the database.
     pub fn index(&self) -> u16 {
         self.index

src/tests/reader.rs

@@ -169,6 +169,23 @@ fn two_dimension_on_a_column() {
     "###);
 }
 
+#[test]
+fn get_item_ids() {
+    let handle = create_database();
+    let mut wtxn = handle.env.write_txn().unwrap();
+    let writer = Writer::new(handle.database, 0, 2);
+    for i in 0..10 {
+        writer.add_item(&mut wtxn, i, &[0.0, i as f32]).unwrap();
+    }
+
+    writer.build(&mut wtxn, &mut rng(), Some(50)).unwrap();
+
+    let reader = Reader::<Euclidean>::open(&wtxn, 0, handle.database).unwrap();
+    let ret = reader.item_ids();
+
+    insta::assert_debug_snapshot!(ret, @"RoaringBitmap<[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>");
+}
+
 #[test]
 fn filtering() {
     let handle = create_database();