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9a5886bd8c
Summary: Current implementation of the ```read_options.deadline``` option only checks the deadline for random file reads during point lookups. This PR extends the checks to file opens, prefetches and preloads as part of table open. The main changes are in the ```BlockBasedTable```, partitioned index and filter readers, and ```TableCache``` to take ReadOptions as an additional parameter. In ```BlockBasedTable::Open```, in order to retain existing behavior w.r.t checksum verification and block cache usage, we filter out most of the options in ```ReadOptions``` except ```deadline```. However, having the ```ReadOptions``` gives us more flexibility to honor other options like verify_checksums, fill_cache etc. in the future. Additional changes in callsites due to function signature changes in ```NewTableReader()``` and ```FilePrefetchBuffer```. Pull Request resolved: https://github.com/facebook/rocksdb/pull/6982 Test Plan: Add new unit tests in db_basic_test Reviewed By: riversand963 Differential Revision: D22219515 Pulled By: anand1976 fbshipit-source-id: 8a3b92f4a889808013838603aa3ca35229cd501b
100 lines
4.2 KiB
C++
100 lines
4.2 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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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#pragma once
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#include <atomic>
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#include <sstream>
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#include <string>
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#include "file/random_access_file_reader.h"
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#include "port/port.h"
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#include "rocksdb/env.h"
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#include "rocksdb/options.h"
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#include "util/aligned_buffer.h"
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namespace ROCKSDB_NAMESPACE {
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// FilePrefetchBuffer is a smart buffer to store and read data from a file.
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class FilePrefetchBuffer {
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public:
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// Constructor.
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//
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// All arguments are optional.
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// file_reader : the file reader to use. Can be a nullptr.
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// readahead_size : the initial readahead size.
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// max_readahead_size : the maximum readahead size.
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// If max_readahead_size > readahead_size, the readahead size will be
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// doubled on every IO until max_readahead_size is hit.
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// Typically this is set as a multiple of readahead_size.
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// max_readahead_size should be greater than equal to readahead_size.
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// enable : controls whether reading from the buffer is enabled.
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// If false, TryReadFromCache() always return false, and we only take stats
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// for the minimum offset if track_min_offset = true.
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// track_min_offset : Track the minimum offset ever read and collect stats on
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// it. Used for adaptable readahead of the file footer/metadata.
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//
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// Automatic readhead is enabled for a file if file_reader, readahead_size,
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// and max_readahead_size are passed in.
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// If file_reader is a nullptr, setting readadhead_size and max_readahead_size
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// does not make any sense. So it does nothing.
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// A user can construct a FilePrefetchBuffer without any arguments, but use
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// `Prefetch` to load data into the buffer.
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FilePrefetchBuffer(RandomAccessFileReader* file_reader = nullptr,
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size_t readadhead_size = 0, size_t max_readahead_size = 0,
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bool enable = true, bool track_min_offset = false)
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: buffer_offset_(0),
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file_reader_(file_reader),
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readahead_size_(readadhead_size),
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max_readahead_size_(max_readahead_size),
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min_offset_read_(port::kMaxSizet),
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enable_(enable),
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track_min_offset_(track_min_offset) {}
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// Load data into the buffer from a file.
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// reader : the file reader.
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// offset : the file offset to start reading from.
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// n : the number of bytes to read.
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// for_compaction : if prefetch is done for compaction read.
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Status Prefetch(const IOOptions& opts, RandomAccessFileReader* reader,
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uint64_t offset, size_t n, bool for_compaction = false);
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// Tries returning the data for a file raed from this buffer, if that data is
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// in the buffer.
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// It handles tracking the minimum read offset if track_min_offset = true.
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// It also does the exponential readahead when readadhead_size is set as part
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// of the constructor.
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//
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// offset : the file offset.
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// n : the number of bytes.
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// result : output buffer to put the data into.
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// for_compaction : if cache read is done for compaction read.
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bool TryReadFromCache(const IOOptions& opts, uint64_t offset, size_t n,
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Slice* result, bool for_compaction = false);
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// The minimum `offset` ever passed to TryReadFromCache(). This will nly be
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// tracked if track_min_offset = true.
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size_t min_offset_read() const { return min_offset_read_; }
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private:
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AlignedBuffer buffer_;
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uint64_t buffer_offset_;
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RandomAccessFileReader* file_reader_;
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size_t readahead_size_;
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size_t max_readahead_size_;
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// The minimum `offset` ever passed to TryReadFromCache().
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size_t min_offset_read_;
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// if false, TryReadFromCache() always return false, and we only take stats
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// for track_min_offset_ if track_min_offset_ = true
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bool enable_;
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// If true, track minimum `offset` ever passed to TryReadFromCache(), which
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// can be fetched from min_offset_read().
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bool track_min_offset_;
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};
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} // namespace ROCKSDB_NAMESPACE
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