mirror of
https://github.com/matrix-construct/construct
synced 2024-10-30 02:18:58 +01:00
68 lines
2.2 KiB
C++
68 lines
2.2 KiB
C++
// Matrix Construct
|
|
//
|
|
// Copyright (C) Matrix Construct Developers, Authors & Contributors
|
|
// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
|
|
//
|
|
// Permission to use, copy, modify, and/or distribute this software for any
|
|
// purpose with or without fee is hereby granted, provided that the above
|
|
// copyright notice and this permission notice is present in all copies. The
|
|
// full license for this software is available in the LICENSE file.
|
|
|
|
#pragma once
|
|
#define HAVE_IRCD_DB_COMPACTOR_H
|
|
|
|
namespace ircd::db
|
|
{
|
|
struct compactor;
|
|
}
|
|
|
|
/// Compaction callback
|
|
///
|
|
/// return db::op::GET (0) from callback for no-op
|
|
/// return db::op::DELETE from callback to delete this kv.
|
|
/// return db::op::SET from callback if replacement modified.
|
|
/// return db::op::DELETE_RANGE from callback if skip_until modified.
|
|
///
|
|
/// Please note the exact mechanism of the return value from the closure. This
|
|
/// is an operation during a specific compaction, not a front-end operation on
|
|
/// the database.
|
|
///
|
|
/// - op::GET the source record is moved to the target as per normal
|
|
/// compaction.
|
|
///
|
|
/// - op::SET the new value is placed in the compaction target rather than
|
|
/// the source value. Specify the new value at `replace` in the args struct.
|
|
///
|
|
/// - op::DELETE a delete record is placed in the compaction target and the
|
|
/// source value will be forgotten.
|
|
///
|
|
/// - op::DELETE_RANGE skips moving the source record to the target. The
|
|
/// source record is simply forgotten without a delete record. User can set
|
|
/// `skip_until` in the args structure to apply this non-action to a range.
|
|
///
|
|
struct ircd::db::compactor
|
|
{
|
|
struct args;
|
|
using proto = db::op (const args &);
|
|
using callback = std::function<proto>;
|
|
|
|
callback value;
|
|
callback merge;
|
|
};
|
|
|
|
/// The arguments presented to the callback are aggregated in this structure.
|
|
///
|
|
/// For each record iterated in the compaction we present const information
|
|
/// for examination by the user in the first part of this structure. It also
|
|
/// contains an interface for the compactor to mutate records during the
|
|
/// process.
|
|
///
|
|
struct ircd::db::compactor::args
|
|
{
|
|
const int &level;
|
|
const string_view key;
|
|
const string_view val;
|
|
|
|
std::string *const &replace;
|
|
std::string *const &skip_until;
|
|
};
|