| // Copyright (c) 2011-present, Facebook, Inc. All rights reserved. |
| // This source code is licensed under both the GPLv2 (found in the |
| // COPYING file in the root directory) and Apache 2.0 License |
| // (found in the LICENSE.Apache file in the root directory). |
| // |
| // Copyright (c) 2012 The LevelDB Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. See the AUTHORS file for names of contributors. |
| // |
| // A filter block is stored near the end of a Table file. It contains |
| // filters (e.g., bloom filters) for all data blocks in the table combined |
| // into a single filter block. |
| |
| #pragma once |
| |
| #include <stddef.h> |
| #include <stdint.h> |
| #include <string> |
| #include <memory> |
| #include <vector> |
| #include "rocksdb/options.h" |
| #include "rocksdb/slice.h" |
| #include "rocksdb/slice_transform.h" |
| #include "table/filter_block.h" |
| #include "util/hash.h" |
| |
| namespace rocksdb { |
| |
| |
| // A BlockBasedFilterBlockBuilder is used to construct all of the filters for a |
| // particular Table. It generates a single string which is stored as |
| // a special block in the Table. |
| // |
| // The sequence of calls to BlockBasedFilterBlockBuilder must match the regexp: |
| // (StartBlock Add*)* Finish |
| class BlockBasedFilterBlockBuilder : public FilterBlockBuilder { |
| public: |
| BlockBasedFilterBlockBuilder(const SliceTransform* prefix_extractor, |
| const BlockBasedTableOptions& table_opt); |
| |
| virtual bool IsBlockBased() override { return true; } |
| virtual void StartBlock(uint64_t block_offset) override; |
| virtual void Add(const Slice& key) override; |
| virtual Slice Finish(const BlockHandle& tmp, Status* status) override; |
| using FilterBlockBuilder::Finish; |
| |
| private: |
| void AddKey(const Slice& key); |
| void AddPrefix(const Slice& key); |
| void GenerateFilter(); |
| |
| // important: all of these might point to invalid addresses |
| // at the time of destruction of this filter block. destructor |
| // should NOT dereference them. |
| const FilterPolicy* policy_; |
| const SliceTransform* prefix_extractor_; |
| bool whole_key_filtering_; |
| |
| size_t prev_prefix_start_; // the position of the last appended prefix |
| // to "entries_". |
| size_t prev_prefix_size_; // the length of the last appended prefix to |
| // "entries_". |
| std::string entries_; // Flattened entry contents |
| std::vector<size_t> start_; // Starting index in entries_ of each entry |
| std::string result_; // Filter data computed so far |
| std::vector<Slice> tmp_entries_; // policy_->CreateFilter() argument |
| std::vector<uint32_t> filter_offsets_; |
| |
| // No copying allowed |
| BlockBasedFilterBlockBuilder(const BlockBasedFilterBlockBuilder&); |
| void operator=(const BlockBasedFilterBlockBuilder&); |
| }; |
| |
| // A FilterBlockReader is used to parse filter from SST table. |
| // KeyMayMatch and PrefixMayMatch would trigger filter checking |
| class BlockBasedFilterBlockReader : public FilterBlockReader { |
| public: |
| // REQUIRES: "contents" and *policy must stay live while *this is live. |
| BlockBasedFilterBlockReader(const SliceTransform* prefix_extractor, |
| const BlockBasedTableOptions& table_opt, |
| bool whole_key_filtering, |
| BlockContents&& contents, Statistics* statistics); |
| virtual bool IsBlockBased() override { return true; } |
| virtual bool KeyMayMatch( |
| const Slice& key, uint64_t block_offset = kNotValid, |
| const bool no_io = false, |
| const Slice* const const_ikey_ptr = nullptr) override; |
| virtual bool PrefixMayMatch( |
| const Slice& prefix, uint64_t block_offset = kNotValid, |
| const bool no_io = false, |
| const Slice* const const_ikey_ptr = nullptr) override; |
| virtual size_t ApproximateMemoryUsage() const override; |
| |
| // convert this object to a human readable form |
| std::string ToString() const override; |
| |
| private: |
| const FilterPolicy* policy_; |
| const SliceTransform* prefix_extractor_; |
| const char* data_; // Pointer to filter data (at block-start) |
| const char* offset_; // Pointer to beginning of offset array (at block-end) |
| size_t num_; // Number of entries in offset array |
| size_t base_lg_; // Encoding parameter (see kFilterBaseLg in .cc file) |
| BlockContents contents_; |
| |
| bool MayMatch(const Slice& entry, uint64_t block_offset); |
| |
| // No copying allowed |
| BlockBasedFilterBlockReader(const BlockBasedFilterBlockReader&); |
| void operator=(const BlockBasedFilterBlockReader&); |
| }; |
| } // namespace rocksdb |