fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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87 lines
3.3 KiB
87 lines
3.3 KiB
// Copyright (c) 2021, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#pragma once
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#include <stdint.h>
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#include <memory>
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#include <string>
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#include "rocksdb/cache.h"
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#include "rocksdb/customizable.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/statistics.h"
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#include "rocksdb/status.h"
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namespace ROCKSDB_NAMESPACE {
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// A handle for lookup result. The handle may not be immediately ready or
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// have a valid value. The caller must call isReady() to determine if its
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// ready, and call Wait() in order to block until it becomes ready.
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// The caller must call value() after it becomes ready to determine if the
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// handle successfullly read the item.
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class SecondaryCacheResultHandle {
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public:
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virtual ~SecondaryCacheResultHandle() {}
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// Returns whether the handle is ready or not
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virtual bool IsReady() = 0;
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// Block until handle becomes ready
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virtual void Wait() = 0;
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// Return the value. If nullptr, it means the lookup was unsuccessful
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virtual void* Value() = 0;
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// Return the size of value
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virtual size_t Size() = 0;
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};
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// SecondaryCache
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//
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// Cache interface for caching blocks on a secondary tier (which can include
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// non-volatile media, or alternate forms of caching such as compressed data)
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//
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// Exceptions MUST NOT propagate out of overridden functions into RocksDB,
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// because RocksDB is not exception-safe. This could cause undefined behavior
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// including data loss, unreported corruption, deadlocks, and more.
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class SecondaryCache : public Customizable {
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public:
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virtual ~SecondaryCache() {}
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static const char* Type() { return "SecondaryCache"; }
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static Status CreateFromString(const ConfigOptions& config_options,
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const std::string& id,
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std::shared_ptr<SecondaryCache>* result);
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// Insert the given value into this cache. The value is not written
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// directly. Rather, the SaveToCallback provided by helper_cb will be
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// used to extract the persistable data in value, which will be written
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// to this tier. The implementation may or may not write it to cache
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// depending on the admission control policy, even if the return status is
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// success.
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virtual Status Insert(const Slice& key, void* value,
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const Cache::CacheItemHelper* helper) = 0;
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// Lookup the data for the given key in this cache. The create_cb
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// will be used to create the object. The handle returned may not be
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// ready yet, unless wait=true, in which case Lookup() will block until
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// the handle is ready. is_in_sec_cache is to indicate whether the
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// handle is possibly erased from the secondary cache after the Lookup.
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virtual std::unique_ptr<SecondaryCacheResultHandle> Lookup(
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const Slice& key, const Cache::CreateCallback& create_cb, bool wait,
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bool& is_in_sec_cache) = 0;
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// At the discretion of the implementation, erase the data associated
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// with key
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virtual void Erase(const Slice& key) = 0;
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// Wait for a collection of handles to become ready
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virtual void WaitAll(std::vector<SecondaryCacheResultHandle*> handles) = 0;
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virtual std::string GetPrintableOptions() const override = 0;
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};
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} // namespace ROCKSDB_NAMESPACE
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