e8cb32ed67
Summary: The patch adds blob file support to the `Get` API by extending `Version` so that whenever a blob reference is read from a file, the blob is retrieved from the corresponding blob file and passed back to the caller. (This is assuming the blob reference is valid and the blob file is actually part of the given `Version`.) It also introduces a cache of `BlobFileReader`s called `BlobFileCache` that enables sharing `BlobFileReader`s between callers. `BlobFileCache` uses the same backing cache as `TableCache`, so `max_open_files` (if specified) limits the total number of open (table + blob) files. TODO: proactively open/cache blob files and pin the cache handles of the readers in the metadata objects similarly to what `VersionBuilder::LoadTableHandlers` does for table files. Pull Request resolved: https://github.com/facebook/rocksdb/pull/7540 Test Plan: `make check` Reviewed By: riversand963 Differential Revision: D24260219 Pulled By: ltamasi fbshipit-source-id: a8a2a4f11d3d04d6082201b52184bc4d7b0857ba
115 lines
2.8 KiB
C++
115 lines
2.8 KiB
C++
// Copyright (c) 2011-present, 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 <cassert>
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#include "rocksdb/cache.h"
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#include "rocksdb/rocksdb_namespace.h"
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namespace ROCKSDB_NAMESPACE {
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// Returns the cached value given a cache handle.
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template <typename T>
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T* GetFromCacheHandle(Cache* cache, Cache::Handle* handle) {
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assert(cache);
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assert(handle);
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return static_cast<T*>(cache->Value(handle));
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}
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// Simple generic deleter for Cache (to be used with Cache::Insert).
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template <typename T>
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void DeleteCacheEntry(const Slice& /* key */, void* value) {
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delete static_cast<T*>(value);
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}
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// Turns a T* into a Slice so it can be used as a key with Cache.
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template <typename T>
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Slice GetSlice(const T* t) {
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return Slice(reinterpret_cast<const char*>(t), sizeof(T));
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}
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// Generic resource management object for cache handles that releases the handle
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// when destroyed. Has unique ownership of the handle, so copying it is not
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// allowed, while moving it transfers ownership.
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template <typename T>
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class CacheHandleGuard {
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public:
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CacheHandleGuard() = default;
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CacheHandleGuard(Cache* cache, Cache::Handle* handle)
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: cache_(cache),
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handle_(handle),
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value_(GetFromCacheHandle<T>(cache, handle)) {
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assert(cache_ && handle_ && value_);
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}
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CacheHandleGuard(const CacheHandleGuard&) = delete;
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CacheHandleGuard& operator=(const CacheHandleGuard&) = delete;
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CacheHandleGuard(CacheHandleGuard&& rhs) noexcept
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: cache_(rhs.cache_), handle_(rhs.handle_), value_(rhs.value_) {
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assert((!cache_ && !handle_ && !value_) || (cache_ && handle_ && value_));
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rhs.ResetFields();
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}
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CacheHandleGuard& operator=(CacheHandleGuard&& rhs) noexcept {
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if (this == &rhs) {
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return *this;
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}
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ReleaseHandle();
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cache_ = rhs.cache_;
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handle_ = rhs.handle_;
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value_ = rhs.value_;
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assert((!cache_ && !handle_ && !value_) || (cache_ && handle_ && value_));
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rhs.ResetFields();
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return *this;
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}
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~CacheHandleGuard() { ReleaseHandle(); }
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bool IsEmpty() const { return !handle_; }
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Cache* GetCache() const { return cache_; }
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Cache::Handle* GetCacheHandle() const { return handle_; }
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T* GetValue() const { return value_; }
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void Reset() {
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ReleaseHandle();
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ResetFields();
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}
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private:
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void ReleaseHandle() {
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if (IsEmpty()) {
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return;
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}
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assert(cache_);
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cache_->Release(handle_);
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}
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void ResetFields() {
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cache_ = nullptr;
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handle_ = nullptr;
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value_ = nullptr;
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}
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private:
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Cache* cache_ = nullptr;
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Cache::Handle* handle_ = nullptr;
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T* value_ = nullptr;
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};
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} // namespace ROCKSDB_NAMESPACE
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