// Copyright (C) Parity Technologies (UK) Ltd.
// This file is part of Polkadot.
// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Polkadot. If not, see <http://www.gnu.org/licenses/>.
//! Approval DB accessors and writers for on-disk persisted approval storage
//! data.
//!
//! We persist data to disk although it is not intended to be used across runs of the
//! program. This is because under medium to long periods of finality stalling, for whatever
//! reason that may be, the amount of data we'd need to keep would be potentially too large
//! for memory.
//!
//! With tens or hundreds of parachains, hundreds of validators, and parablocks
//! in every relay chain block, there can be a humongous amount of information to reference
//! at any given time.
//!
//! As such, we provide a function from this module to clear the database on start-up.
//! In the future, we may use a temporary DB which doesn't need to be wiped, but for the
//! time being we share the same DB with the rest of Substrate.