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// Copyright 2020-2021 IOTA Stiftung
// SPDX-License-Identifier: Apache-2.0

use crate::backend::StorageBackend;

/// `MultiFetch<'a, K, V>` trait extends the `StorageBackend` with `multi_fetch` operation for the (key: K, value: V)
/// pair; therefore, it should be explicitly implemented for the corresponding `StorageBackend`.
pub trait MultiFetch<'a, K, V>: StorageBackend {
    /// The iterator associated type over values.
    type Iter: 'a + Iterator<Item = Result<Option<V>, Self::Error>>;

    /// Fetches the values associated with the keys from the storage.
    fn multi_fetch(&'a self, keys: &'a [K]) -> Result<Self::Iter, Self::Error>;
}