Summary:
1. Make filter_block.h a base class. Derive block_based_filter_block and full_filter_block. The previous one is the traditional filter block. The full_filter_block is newly added. It would generate a filter block that contain all the keys in SST file.
2. When querying a key, table would first check if full_filter is available. If not, it would go to the exact data block and check using block_based filter.
3. User could choose to use full_filter or tradional(block_based_filter). They would be stored in SST file with different meta index name. "filter.filter_policy" or "full_filter.filter_policy". Then, Table reader is able to know the fllter block type.
4. Some optimizations have been done for full_filter_block, thus it requires a different interface compared to the original one in filter_policy.h.
5. Actual implementation of filter bits coding/decoding is placed in util/bloom_impl.cc
Benchmark: base commit 1d23b5c470
Command:
db_bench --db=/dev/shm/rocksdb --num_levels=6 --key_size=20 --prefix_size=20 --keys_per_prefix=0 --value_size=100 --write_buffer_size=134217728 --max_write_buffer_number=2 --target_file_size_base=33554432 --max_bytes_for_level_base=1073741824 --verify_checksum=false --max_background_compactions=4 --use_plain_table=0 --memtablerep=prefix_hash --open_files=-1 --mmap_read=1 --mmap_write=0 --bloom_bits=10 --bloom_locality=1 --memtable_bloom_bits=500000 --compression_type=lz4 --num=393216000 --use_hash_search=1 --block_size=1024 --block_restart_interval=16 --use_existing_db=1 --threads=1 --benchmarks=readrandom —disable_auto_compactions=1
Read QPS increase for about 30% from 2230002 to 2991411.
Test Plan:
make all check
valgrind db_test
db_stress --use_block_based_filter = 0
./auto_sanity_test.sh
Reviewers: igor, yhchiang, ljin, sdong
Reviewed By: sdong
Subscribers: dhruba, leveldb
Differential Revision: https://reviews.facebook.net/D20979
108 lines
3.9 KiB
C++
108 lines
3.9 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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#include <stddef.h>
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#include <stdint.h>
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#include <memory>
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#include <string>
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#include <vector>
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#include "rocksdb/options.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/slice_transform.h"
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#include "db/dbformat.h"
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#include "util/hash.h"
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#include "table/filter_block.h"
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namespace rocksdb {
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class FilterPolicy;
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class FilterBitsBuilder;
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class FilterBitsReader;
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// A FullFilterBlockBuilder is used to construct a full filter for a
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// particular Table. It generates a single string which is stored as
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// a special block in the Table.
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// The format of full filter block is:
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// +----------------------------------------------------------------+
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// | full filter for all keys in sst file |
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// +----------------------------------------------------------------+
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// The full filter can be very large. At the end of it, we put
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// num_probes: how many hash functions are used in bloom filter
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//
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class FullFilterBlockBuilder : public FilterBlockBuilder {
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public:
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explicit FullFilterBlockBuilder(const SliceTransform* prefix_extractor,
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const BlockBasedTableOptions& table_opt,
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FilterBitsBuilder* filter_bits_builder);
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// bits_builder is created in filter_policy, it should be passed in here
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// directly. and be deleted here
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~FullFilterBlockBuilder() {}
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virtual bool IsBlockBased() override { return false; }
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virtual void StartBlock(uint64_t block_offset) override {}
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virtual void Add(const Slice& key) override;
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virtual Slice Finish() override;
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private:
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// important: all of these might point to invalid addresses
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// at the time of destruction of this filter block. destructor
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// should NOT dereference them.
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const SliceTransform* prefix_extractor_;
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bool whole_key_filtering_;
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uint32_t num_added_;
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std::unique_ptr<FilterBitsBuilder> filter_bits_builder_;
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std::unique_ptr<const char[]> filter_data;
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void AddKey(const Slice& key);
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void AddPrefix(const Slice& key);
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// No copying allowed
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FullFilterBlockBuilder(const FullFilterBlockBuilder&);
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void operator=(const FullFilterBlockBuilder&);
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};
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// A FilterBlockReader is used to parse filter from SST table.
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// KeyMayMatch and PrefixMayMatch would trigger filter checking
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class FullFilterBlockReader : public FilterBlockReader {
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public:
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// REQUIRES: "contents" and filter_bits_reader must stay live
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// while *this is live.
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explicit FullFilterBlockReader(const SliceTransform* prefix_extractor,
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const BlockBasedTableOptions& table_opt,
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const Slice& contents,
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FilterBitsReader* filter_bits_reader,
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bool delete_contents_after_use = false);
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// bits_reader is created in filter_policy, it should be passed in here
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// directly. and be deleted here
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~FullFilterBlockReader() {}
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virtual bool IsBlockBased() override { return false; }
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virtual bool KeyMayMatch(const Slice& key,
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uint64_t block_offset = kNotValid) override;
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virtual bool PrefixMayMatch(const Slice& prefix,
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uint64_t block_offset = kNotValid) override;
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virtual size_t ApproximateMemoryUsage() const override;
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private:
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const SliceTransform* prefix_extractor_;
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bool whole_key_filtering_;
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std::unique_ptr<FilterBitsReader> filter_bits_reader_;
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Slice contents_;
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std::unique_ptr<const char[]> filter_data;
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bool MayMatch(const Slice& entry);
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// No copying allowed
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FullFilterBlockReader(const FullFilterBlockReader&);
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void operator=(const FullFilterBlockReader&);
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};
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} // namespace rocksdb
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