Add Storage::range_keys and Storage::range_values

CHANGELOG.md

@@ -20,6 +20,9 @@ and this project adheres to
 - cosmwasm-std: Add `FromStr` impl for `Coin`. ([#1684])
 - cosmwasm-std: Add `Decimal::bps` and `Decimal256::bps` to create a decimal
   from a basis point value ([#1715]).
+- cosmwasm-std: Add trait functions `Storage::range_keys` and
+  `Storage::range_values`. The default implementations just use
+  `Storage::range`. Later this can be implemented more efficiently.
 
 [#1635]: https://github.com/CosmWasm/cosmwasm/pull/1635
 [#1647]: https://github.com/CosmWasm/cosmwasm/pull/1647

packages/std/src/traits.rs

@@ -38,19 +38,52 @@ pub trait Storage {
     /// is not great yet and might not be possible in all backends. But we're trying to get there.
     fn get(&self, key: &[u8]) -> Option<Vec<u8>>;
 
-    #[cfg(feature = "iterator")]
     /// Allows iteration over a set of key/value pairs, either forwards or backwards.
     ///
     /// The bound `start` is inclusive and `end` is exclusive.
-    ///
     /// If `start` is lexicographically greater than or equal to `end`, an empty range is described, mo matter of the order.
+    #[cfg(feature = "iterator")]
     fn range<'a>(
         &'a self,
         start: Option<&[u8]>,
         end: Option<&[u8]>,
         order: Order,
     ) -> Box<dyn Iterator<Item = Record> + 'a>;
 
+    /// Allows iteration over a set of keys, either forwards or backwards.
+    ///
+    /// The bound `start` is inclusive and `end` is exclusive.
+    /// If `start` is lexicographically greater than or equal to `end`, an empty range is described, mo matter of the order.
+    ///
+    /// The default implementation uses [`Storage::range`] and discards the values. More efficient
+    /// implementations might be possible depending on the storage.
+    #[cfg(feature = "iterator")]
+    fn range_keys<'a>(
+        &'a self,
+        start: Option<&[u8]>,
+        end: Option<&[u8]>,
+        order: Order,
+    ) -> Box<dyn Iterator<Item = Vec<u8>> + 'a> {
+        Box::new(self.range(start, end, order).map(|(k, _v)| k))
+    }
+
+    /// Allows iteration over a set of values, either forwards or backwards.
+    ///
+    /// The bound `start` is inclusive and `end` is exclusive.
+    /// If `start` is lexicographically greater than or equal to `end`, an empty range is described, mo matter of the order.
+    ///
+    /// The default implementation uses [`Storage::range`] and discards the keys. More efficient implementations
+    /// might be possible depending on the storage.
+    #[cfg(feature = "iterator")]
+    fn range_values<'a>(
+        &'a self,
+        start: Option<&[u8]>,
+        end: Option<&[u8]>,
+        order: Order,
+    ) -> Box<dyn Iterator<Item = Vec<u8>> + 'a> {
+        Box::new(self.range(start, end, order).map(|(_k, v)| v))
+    }
+
     fn set(&mut self, key: &[u8], value: &[u8]);
 
     /// Removes a database entry at `key`.