Add ReadableTable::first() and last()

src/table.rs

@@ -292,6 +292,16 @@ pub trait ReadableTable<K: RedbKey + 'static, V: RedbValue + 'static>: Sealed {
         K: 'a,
         KR: Borrow<K::SelfType<'a>> + 'a;
 
+    /// Returns the first key-value pair in the table, if it exists
+    fn first(&self) -> Result<Option<(AccessGuard<K>, AccessGuard<V>)>> {
+        self.iter()?.next().transpose()
+    }
+
+    /// Returns the last key-value pair in the table, if it exists
+    fn last(&self) -> Result<Option<(AccessGuard<K>, AccessGuard<V>)>> {
+        self.iter()?.next_back().transpose()
+    }
+
     /// Retrieves information about storage usage for the table
     fn stats(&self) -> Result<TableStats>;
 

tests/basic_tests.rs

@@ -36,6 +36,29 @@ fn len() {
     assert_eq!(table.len().unwrap(), 3);
 }
 
+#[test]
+fn first_last() {
+    let tmpfile = create_tempfile();
+    let db = Database::create(tmpfile.path()).unwrap();
+    let write_txn = db.begin_write().unwrap();
+    {
+        let mut table = write_txn.open_table(STR_TABLE).unwrap();
+        assert!(table.first().unwrap().is_none());
+        assert!(table.last().unwrap().is_none());
+        table.insert("a", "world1").unwrap();
+        assert_eq!(table.first().unwrap().unwrap().0.value(), "a");
+        assert_eq!(table.last().unwrap().unwrap().0.value(), "a");
+        table.insert("b", "world2").unwrap();
+        table.insert("c", "world3").unwrap();
+    }
+    write_txn.commit().unwrap();
+
+    let read_txn = db.begin_read().unwrap();
+    let table = read_txn.open_table(STR_TABLE).unwrap();
+    assert_eq!(table.first().unwrap().unwrap().0.value(), "a");
+    assert_eq!(table.last().unwrap().unwrap().0.value(), "c");
+}
+
 #[test]
 fn pop() {
     let tmpfile = create_tempfile();