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35ad531be3
Summary: Separate a new class InternalIterator from class Iterator, when the look-up is done internally, which also means they operate on key with sequence ID and type. This change will enable potential future optimizations but for now InternalIterator's functions are still the same as Iterator's. At the same time, separate the cleanup function to a separate class and let both of InternalIterator and Iterator inherit from it. Test Plan: Run all existing tests. Reviewers: igor, yhchiang, anthony, kradhakrishnan, IslamAbdelRahman, rven Reviewed By: rven Subscribers: leveldb, dhruba Differential Revision: https://reviews.facebook.net/D48549
87 lines
3 KiB
C++
87 lines
3 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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#pragma once
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#include <string>
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#include <unordered_map>
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#include "rocksdb/status.h"
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#include "util/arena.h"
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#include "util/murmurhash.h"
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namespace rocksdb {
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class Comparator;
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class InternalIterator;
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class Slice;
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class SliceTransform;
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// Build a hash-based index to speed up the lookup for "index block".
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// BlockHashIndex accepts a key and, if found, returns its restart index within
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// that index block.
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class BlockHashIndex {
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public:
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// Represents a restart index in the index block's restart array.
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struct RestartIndex {
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explicit RestartIndex(uint32_t _first_index, uint32_t _num_blocks = 1)
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: first_index(_first_index), num_blocks(_num_blocks) {}
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// For a given prefix, what is the restart index for the first data block
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// that contains it.
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uint32_t first_index = 0;
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// How many data blocks contains this prefix?
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uint32_t num_blocks = 1;
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};
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// @params own_prefixes indicate if we should take care the memory space for
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// the `key_prefix`
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// passed by Add()
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explicit BlockHashIndex(const SliceTransform* hash_key_extractor,
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bool own_prefixes)
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: hash_key_extractor_(hash_key_extractor), kOwnPrefixes(own_prefixes) {}
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// Maps a key to its restart first_index.
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// Returns nullptr if the restart first_index is found
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const RestartIndex* GetRestartIndex(const Slice& key);
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bool Add(const Slice& key_prefix, uint32_t restart_index,
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uint32_t num_blocks);
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size_t ApproximateMemoryUsage() const {
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return arena_.ApproximateMemoryUsage();
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}
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private:
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const SliceTransform* hash_key_extractor_;
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std::unordered_map<Slice, RestartIndex, murmur_hash> restart_indices_;
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Arena arena_;
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bool kOwnPrefixes;
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};
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// Create hash index by reading from the metadata blocks.
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// @params prefixes: a sequence of prefixes.
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// @params prefix_meta: contains the "metadata" to of the prefixes.
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Status CreateBlockHashIndex(const SliceTransform* hash_key_extractor,
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const Slice& prefixes, const Slice& prefix_meta,
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BlockHashIndex** hash_index);
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// Create hash index by scanning the entries in index as well as the whole
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// dataset.
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// @params index_iter: an iterator with the pointer to the first entry in a
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// block.
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// @params data_iter: an iterator that can scan all the entries reside in a
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// table.
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// @params num_restarts: used for correctness verification.
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// @params hash_key_extractor: extract the hashable part of a given key.
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// On error, nullptr will be returned.
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BlockHashIndex* CreateBlockHashIndexOnTheFly(
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InternalIterator* index_iter, InternalIterator* data_iter,
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const uint32_t num_restarts, const Comparator* comparator,
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const SliceTransform* hash_key_extractor);
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} // namespace rocksdb
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