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https://github.com/facebook/rocksdb.git
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7f71448388
Summary: This implements a cache friendly version of Cuckoo Hash in which, in case of collission, we try to insert in next few locations. The size of the neighborhood to check is taken as an input parameter in builder and stored in the table.
Test Plan:
make check all
cuckoo_table_{db,reader,builder}_test
Reviewers: sdong, ljin
Reviewed By: ljin
Subscribers: leveldb
Differential Revision: https://reviews.facebook.net/D22455
105 lines
3.5 KiB
C++
105 lines
3.5 KiB
C++
// Copyright (c) 2014, 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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#ifndef ROCKSDB_LITE
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#include <stdint.h>
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#include <limits>
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#include <string>
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#include <utility>
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#include <vector>
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#include "rocksdb/status.h"
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#include "table/table_builder.h"
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#include "rocksdb/table.h"
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#include "rocksdb/table_properties.h"
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#include "util/autovector.h"
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namespace rocksdb {
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class CuckooTableBuilder: public TableBuilder {
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public:
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CuckooTableBuilder(
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WritableFile* file, double hash_table_ratio, uint32_t max_num_hash_table,
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uint32_t max_search_depth, const Comparator* user_comparator,
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uint32_t cuckoo_block_size,
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uint64_t (*get_slice_hash)(const Slice&, uint32_t, uint64_t));
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// REQUIRES: Either Finish() or Abandon() has been called.
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~CuckooTableBuilder() {}
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// Add key,value to the table being constructed.
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// REQUIRES: key is after any previously added key according to comparator.
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// REQUIRES: Finish(), Abandon() have not been called
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void Add(const Slice& key, const Slice& value) override;
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// Return non-ok iff some error has been detected.
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Status status() const override { return status_; }
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// Finish building the table. Stops using the file passed to the
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// constructor after this function returns.
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// REQUIRES: Finish(), Abandon() have not been called
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Status Finish() override;
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// Indicate that the contents of this builder should be abandoned. Stops
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// using the file passed to the constructor after this function returns.
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// If the caller is not going to call Finish(), it must call Abandon()
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// before destroying this builder.
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// REQUIRES: Finish(), Abandon() have not been called
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void Abandon() override;
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// Number of calls to Add() so far.
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uint64_t NumEntries() const override;
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// Size of the file generated so far. If invoked after a successful
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// Finish() call, returns the size of the final generated file.
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uint64_t FileSize() const override;
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private:
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struct CuckooBucket {
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CuckooBucket()
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: vector_idx(kMaxVectorIdx), make_space_for_key_call_id(0) {}
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uint32_t vector_idx;
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// This number will not exceed kvs_.size() + max_num_hash_func_.
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// We assume number of items is <= 2^32.
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uint32_t make_space_for_key_call_id;
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};
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static const uint32_t kMaxVectorIdx = std::numeric_limits<int32_t>::max();
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bool MakeSpaceForKey(
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const autovector<uint64_t>& hash_vals,
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const uint64_t hash_table_size,
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const uint64_t call_id,
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std::vector<CuckooBucket>* buckets,
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uint64_t* bucket_id);
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Status MakeHashTable(std::vector<CuckooBucket>* buckets);
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uint32_t num_hash_func_;
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WritableFile* file_;
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const double hash_table_ratio_;
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const uint32_t max_num_hash_func_;
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const uint32_t max_search_depth_;
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const uint32_t cuckoo_block_size_;
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bool is_last_level_file_;
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Status status_;
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std::vector<std::pair<std::string, std::string>> kvs_;
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TableProperties properties_;
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bool has_seen_first_key_;
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const Comparator* ucomp_;
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uint64_t (*get_slice_hash_)(const Slice& s, uint32_t index,
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uint64_t max_num_buckets);
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std::string largest_user_key_ = "";
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std::string smallest_user_key_ = "";
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bool closed_; // Either Finish() or Abandon() has been called.
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// No copying allowed
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CuckooTableBuilder(const CuckooTableBuilder&) = delete;
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void operator=(const CuckooTableBuilder&) = delete;
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};
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} // namespace rocksdb
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#endif // ROCKSDB_LITE
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