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3f57d84af4
Summary: The patch introduces a new class called `BlobContents`, which represents a single uncompressed blob value. We currently use `std::string` for this purpose; `BlobContents` is somewhat smaller but the primary reason for a dedicated class is that it enables certain improvements and optimizations like eliding a copy when inserting a blob into the cache, using custom allocators, or more control over and better accounting of the memory usage of cached blobs (see https://github.com/facebook/rocksdb/issues/10484). (We plan to implement these in subsequent PRs.) Pull Request resolved: https://github.com/facebook/rocksdb/pull/10571 Test Plan: `make check` Reviewed By: riversand963 Differential Revision: D39000965 Pulled By: ltamasi fbshipit-source-id: f296eddf9dec4fc3e11cad525b462bdf63c78f96
57 lines
1.7 KiB
C++
57 lines
1.7 KiB
C++
// Copyright (c) Meta Platforms, Inc. and affiliates.
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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 <memory>
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#include "memory/memory_allocator.h"
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#include "rocksdb/cache.h"
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#include "rocksdb/rocksdb_namespace.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/status.h"
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namespace ROCKSDB_NAMESPACE {
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// A class representing a single uncompressed value read from a blob file.
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class BlobContents {
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public:
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static std::unique_ptr<BlobContents> Create(CacheAllocationPtr&& allocation,
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size_t size);
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BlobContents(const BlobContents&) = delete;
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BlobContents& operator=(const BlobContents&) = delete;
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BlobContents(BlobContents&&) = default;
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BlobContents& operator=(BlobContents&&) = default;
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~BlobContents() = default;
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const Slice& data() const { return data_; }
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size_t size() const { return data_.size(); }
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// Callbacks for secondary cache
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static size_t SizeCallback(void* obj);
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static Status SaveToCallback(void* from_obj, size_t from_offset,
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size_t length, void* out);
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static void DeleteCallback(const Slice& key, void* value);
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static Cache::CacheItemHelper* GetCacheItemHelper();
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static Status CreateCallback(const void* buf, size_t size, void** out_obj,
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size_t* charge);
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private:
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BlobContents(CacheAllocationPtr&& allocation, size_t size)
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: allocation_(std::move(allocation)), data_(allocation_.get(), size) {}
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CacheAllocationPtr allocation_;
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Slice data_;
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};
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} // namespace ROCKSDB_NAMESPACE
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