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Diffstat (limited to 'src/rocksdb/table/block_based/block_based_table_reader.h')
| -rw-r--r-- | src/rocksdb/table/block_based/block_based_table_reader.h | 824 |
1 files changed, 824 insertions, 0 deletions
diff --git a/src/rocksdb/table/block_based/block_based_table_reader.h b/src/rocksdb/table/block_based/block_based_table_reader.h new file mode 100644 index 000000000..28a378988 --- /dev/null +++ b/src/rocksdb/table/block_based/block_based_table_reader.h @@ -0,0 +1,824 @@ +// 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) 2011 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. + +#pragma once + +#include <stdint.h> +#include <memory> +#include <set> +#include <string> +#include <utility> +#include <vector> + +#include "db/range_tombstone_fragmenter.h" +#include "file/filename.h" +#include "file/random_access_file_reader.h" +#include "options/cf_options.h" +#include "rocksdb/options.h" +#include "rocksdb/persistent_cache.h" +#include "rocksdb/statistics.h" +#include "rocksdb/status.h" +#include "rocksdb/table.h" +#include "table/block_based/block.h" +#include "table/block_based/block_based_table_factory.h" +#include "table/block_based/block_type.h" +#include "table/block_based/cachable_entry.h" +#include "table/block_based/filter_block.h" +#include "table/block_based/uncompression_dict_reader.h" +#include "table/format.h" +#include "table/get_context.h" +#include "table/multiget_context.h" +#include "table/persistent_cache_helper.h" +#include "table/table_properties_internal.h" +#include "table/table_reader.h" +#include "table/two_level_iterator.h" +#include "trace_replay/block_cache_tracer.h" +#include "util/coding.h" +#include "util/user_comparator_wrapper.h" + +namespace ROCKSDB_NAMESPACE { + +class Cache; +class FilterBlockReader; +class BlockBasedFilterBlockReader; +class FullFilterBlockReader; +class Footer; +class InternalKeyComparator; +class Iterator; +class FSRandomAccessFile; +class TableCache; +class TableReader; +class WritableFile; +struct BlockBasedTableOptions; +struct EnvOptions; +struct ReadOptions; +class GetContext; + +typedef std::vector<std::pair<std::string, std::string>> KVPairBlock; + +// Reader class for BlockBasedTable format. +// For the format of BlockBasedTable refer to +// https://github.com/facebook/rocksdb/wiki/Rocksdb-BlockBasedTable-Format. +// This is the default table type. Data is chucked into fixed size blocks and +// each block in-turn stores entries. When storing data, we can compress and/or +// encode data efficiently within a block, which often results in a much smaller +// data size compared with the raw data size. As for the record retrieval, we'll +// first locate the block where target record may reside, then read the block to +// memory, and finally search that record within the block. Of course, to avoid +// frequent reads of the same block, we introduced the block cache to keep the +// loaded blocks in the memory. +class BlockBasedTable : public TableReader { + public: + static const std::string kFilterBlockPrefix; + static const std::string kFullFilterBlockPrefix; + static const std::string kPartitionedFilterBlockPrefix; + // The longest prefix of the cache key used to identify blocks. + // For Posix files the unique ID is three varints. + static const size_t kMaxCacheKeyPrefixSize = kMaxVarint64Length * 3 + 1; + + // All the below fields control iterator readahead + static const size_t kInitAutoReadaheadSize = 8 * 1024; + // Found that 256 KB readahead size provides the best performance, based on + // experiments, for auto readahead. Experiment data is in PR #3282. + static const size_t kMaxAutoReadaheadSize; + static const int kMinNumFileReadsToStartAutoReadahead = 2; + + // Attempt to open the table that is stored in bytes [0..file_size) + // of "file", and read the metadata entries necessary to allow + // retrieving data from the table. + // + // If successful, returns ok and sets "*table_reader" to the newly opened + // table. The client should delete "*table_reader" when no longer needed. + // If there was an error while initializing the table, sets "*table_reader" + // to nullptr and returns a non-ok status. + // + // @param file must remain live while this Table is in use. + // @param prefetch_index_and_filter_in_cache can be used to disable + // prefetching of + // index and filter blocks into block cache at startup + // @param skip_filters Disables loading/accessing the filter block. Overrides + // prefetch_index_and_filter_in_cache, so filter will be skipped if both + // are set. + static Status Open(const ImmutableCFOptions& ioptions, + const EnvOptions& env_options, + const BlockBasedTableOptions& table_options, + const InternalKeyComparator& internal_key_comparator, + std::unique_ptr<RandomAccessFileReader>&& file, + uint64_t file_size, + std::unique_ptr<TableReader>* table_reader, + const SliceTransform* prefix_extractor = nullptr, + bool prefetch_index_and_filter_in_cache = true, + bool skip_filters = false, int level = -1, + const bool immortal_table = false, + const SequenceNumber largest_seqno = 0, + TailPrefetchStats* tail_prefetch_stats = nullptr, + BlockCacheTracer* const block_cache_tracer = nullptr); + + bool PrefixMayMatch(const Slice& internal_key, + const ReadOptions& read_options, + const SliceTransform* options_prefix_extractor, + const bool need_upper_bound_check, + BlockCacheLookupContext* lookup_context) const; + + // Returns a new iterator over the table contents. + // The result of NewIterator() is initially invalid (caller must + // call one of the Seek methods on the iterator before using it). + // @param skip_filters Disables loading/accessing the filter block + // compaction_readahead_size: its value will only be used if caller = + // kCompaction. + InternalIterator* NewIterator(const ReadOptions&, + const SliceTransform* prefix_extractor, + Arena* arena, bool skip_filters, + TableReaderCaller caller, + size_t compaction_readahead_size = 0) override; + + FragmentedRangeTombstoneIterator* NewRangeTombstoneIterator( + const ReadOptions& read_options) override; + + // @param skip_filters Disables loading/accessing the filter block + Status Get(const ReadOptions& readOptions, const Slice& key, + GetContext* get_context, const SliceTransform* prefix_extractor, + bool skip_filters = false) override; + + void MultiGet(const ReadOptions& readOptions, + const MultiGetContext::Range* mget_range, + const SliceTransform* prefix_extractor, + bool skip_filters = false) override; + + // Pre-fetch the disk blocks that correspond to the key range specified by + // (kbegin, kend). The call will return error status in the event of + // IO or iteration error. + Status Prefetch(const Slice* begin, const Slice* end) override; + + // Given a key, return an approximate byte offset in the file where + // the data for that key begins (or would begin if the key were + // present in the file). The returned value is in terms of file + // bytes, and so includes effects like compression of the underlying data. + // E.g., the approximate offset of the last key in the table will + // be close to the file length. + uint64_t ApproximateOffsetOf(const Slice& key, + TableReaderCaller caller) override; + + // Given start and end keys, return the approximate data size in the file + // between the keys. The returned value is in terms of file bytes, and so + // includes effects like compression of the underlying data. + // The start key must not be greater than the end key. + uint64_t ApproximateSize(const Slice& start, const Slice& end, + TableReaderCaller caller) override; + + bool TEST_BlockInCache(const BlockHandle& handle) const; + + // Returns true if the block for the specified key is in cache. + // REQUIRES: key is in this table && block cache enabled + bool TEST_KeyInCache(const ReadOptions& options, const Slice& key); + + // Set up the table for Compaction. Might change some parameters with + // posix_fadvise + void SetupForCompaction() override; + + std::shared_ptr<const TableProperties> GetTableProperties() const override; + + size_t ApproximateMemoryUsage() const override; + + // convert SST file to a human readable form + Status DumpTable(WritableFile* out_file) override; + + Status VerifyChecksum(const ReadOptions& readOptions, + TableReaderCaller caller) override; + + ~BlockBasedTable(); + + bool TEST_FilterBlockInCache() const; + bool TEST_IndexBlockInCache() const; + + // IndexReader is the interface that provides the functionality for index + // access. + class IndexReader { + public: + virtual ~IndexReader() = default; + + // Create an iterator for index access. If iter is null, then a new object + // is created on the heap, and the callee will have the ownership. + // If a non-null iter is passed in, it will be used, and the returned value + // is either the same as iter or a new on-heap object that + // wraps the passed iter. In the latter case the return value points + // to a different object then iter, and the callee has the ownership of the + // returned object. + virtual InternalIteratorBase<IndexValue>* NewIterator( + const ReadOptions& read_options, bool disable_prefix_seek, + IndexBlockIter* iter, GetContext* get_context, + BlockCacheLookupContext* lookup_context) = 0; + + // Report an approximation of how much memory has been used other than + // memory that was allocated in block cache. + virtual size_t ApproximateMemoryUsage() const = 0; + // Cache the dependencies of the index reader (e.g. the partitions + // of a partitioned index). + virtual void CacheDependencies(bool /* pin */) {} + }; + + class IndexReaderCommon; + + static Slice GetCacheKey(const char* cache_key_prefix, + size_t cache_key_prefix_size, + const BlockHandle& handle, char* cache_key); + + // Retrieve all key value pairs from data blocks in the table. + // The key retrieved are internal keys. + Status GetKVPairsFromDataBlocks(std::vector<KVPairBlock>* kv_pair_blocks); + + struct Rep; + + Rep* get_rep() { return rep_; } + const Rep* get_rep() const { return rep_; } + + // input_iter: if it is not null, update this one and return it as Iterator + template <typename TBlockIter> + TBlockIter* NewDataBlockIterator( + const ReadOptions& ro, const BlockHandle& block_handle, + TBlockIter* input_iter, BlockType block_type, GetContext* get_context, + BlockCacheLookupContext* lookup_context, Status s, + FilePrefetchBuffer* prefetch_buffer, bool for_compaction = false) const; + + // input_iter: if it is not null, update this one and return it as Iterator + template <typename TBlockIter> + TBlockIter* NewDataBlockIterator(const ReadOptions& ro, + CachableEntry<Block>& block, + TBlockIter* input_iter, Status s) const; + + class PartitionedIndexIteratorState; + + template <typename TBlocklike> + friend class FilterBlockReaderCommon; + + friend class PartitionIndexReader; + + friend class UncompressionDictReader; + + protected: + Rep* rep_; + explicit BlockBasedTable(Rep* rep, BlockCacheTracer* const block_cache_tracer) + : rep_(rep), block_cache_tracer_(block_cache_tracer) {} + // No copying allowed + explicit BlockBasedTable(const TableReader&) = delete; + void operator=(const TableReader&) = delete; + + private: + friend class MockedBlockBasedTable; + static std::atomic<uint64_t> next_cache_key_id_; + BlockCacheTracer* const block_cache_tracer_; + + void UpdateCacheHitMetrics(BlockType block_type, GetContext* get_context, + size_t usage) const; + void UpdateCacheMissMetrics(BlockType block_type, + GetContext* get_context) const; + void UpdateCacheInsertionMetrics(BlockType block_type, + GetContext* get_context, size_t usage) const; + Cache::Handle* GetEntryFromCache(Cache* block_cache, const Slice& key, + BlockType block_type, + GetContext* get_context) const; + + // Either Block::NewDataIterator() or Block::NewIndexIterator(). + template <typename TBlockIter> + static TBlockIter* InitBlockIterator(const Rep* rep, Block* block, + TBlockIter* input_iter, + bool block_contents_pinned); + + // If block cache enabled (compressed or uncompressed), looks for the block + // identified by handle in (1) uncompressed cache, (2) compressed cache, and + // then (3) file. If found, inserts into the cache(s) that were searched + // unsuccessfully (e.g., if found in file, will add to both uncompressed and + // compressed caches if they're enabled). + // + // @param block_entry value is set to the uncompressed block if found. If + // in uncompressed block cache, also sets cache_handle to reference that + // block. + template <typename TBlocklike> + Status MaybeReadBlockAndLoadToCache( + FilePrefetchBuffer* prefetch_buffer, const ReadOptions& ro, + const BlockHandle& handle, const UncompressionDict& uncompression_dict, + CachableEntry<TBlocklike>* block_entry, BlockType block_type, + GetContext* get_context, BlockCacheLookupContext* lookup_context, + BlockContents* contents) const; + + // Similar to the above, with one crucial difference: it will retrieve the + // block from the file even if there are no caches configured (assuming the + // read options allow I/O). + template <typename TBlocklike> + Status RetrieveBlock(FilePrefetchBuffer* prefetch_buffer, + const ReadOptions& ro, const BlockHandle& handle, + const UncompressionDict& uncompression_dict, + CachableEntry<TBlocklike>* block_entry, + BlockType block_type, GetContext* get_context, + BlockCacheLookupContext* lookup_context, + bool for_compaction, bool use_cache) const; + + void RetrieveMultipleBlocks( + const ReadOptions& options, const MultiGetRange* batch, + const autovector<BlockHandle, MultiGetContext::MAX_BATCH_SIZE>* handles, + autovector<Status, MultiGetContext::MAX_BATCH_SIZE>* statuses, + autovector<CachableEntry<Block>, MultiGetContext::MAX_BATCH_SIZE>* + results, + char* scratch, const UncompressionDict& uncompression_dict) const; + + // Get the iterator from the index reader. + // + // If input_iter is not set, return a new Iterator. + // If input_iter is set, try to update it and return it as Iterator. + // However note that in some cases the returned iterator may be different + // from input_iter. In such case the returned iterator should be freed. + // + // Note: ErrorIterator with Status::Incomplete shall be returned if all the + // following conditions are met: + // 1. We enabled table_options.cache_index_and_filter_blocks. + // 2. index is not present in block cache. + // 3. We disallowed any io to be performed, that is, read_options == + // kBlockCacheTier + InternalIteratorBase<IndexValue>* NewIndexIterator( + const ReadOptions& read_options, bool need_upper_bound_check, + IndexBlockIter* input_iter, GetContext* get_context, + BlockCacheLookupContext* lookup_context) const; + + // Read block cache from block caches (if set): block_cache and + // block_cache_compressed. + // On success, Status::OK with be returned and @block will be populated with + // pointer to the block as well as its block handle. + // @param uncompression_dict Data for presetting the compression library's + // dictionary. + template <typename TBlocklike> + Status GetDataBlockFromCache( + const Slice& block_cache_key, const Slice& compressed_block_cache_key, + Cache* block_cache, Cache* block_cache_compressed, + const ReadOptions& read_options, CachableEntry<TBlocklike>* block, + const UncompressionDict& uncompression_dict, BlockType block_type, + GetContext* get_context) const; + + // Put a raw block (maybe compressed) to the corresponding block caches. + // This method will perform decompression against raw_block if needed and then + // populate the block caches. + // On success, Status::OK will be returned; also @block will be populated with + // uncompressed block and its cache handle. + // + // Allocated memory managed by raw_block_contents will be transferred to + // PutDataBlockToCache(). After the call, the object will be invalid. + // @param uncompression_dict Data for presetting the compression library's + // dictionary. + template <typename TBlocklike> + Status PutDataBlockToCache( + const Slice& block_cache_key, const Slice& compressed_block_cache_key, + Cache* block_cache, Cache* block_cache_compressed, + CachableEntry<TBlocklike>* cached_block, + BlockContents* raw_block_contents, CompressionType raw_block_comp_type, + const UncompressionDict& uncompression_dict, SequenceNumber seq_no, + MemoryAllocator* memory_allocator, BlockType block_type, + GetContext* get_context) const; + + // Calls (*handle_result)(arg, ...) repeatedly, starting with the entry found + // after a call to Seek(key), until handle_result returns false. + // May not make such a call if filter policy says that key is not present. + friend class TableCache; + friend class BlockBasedTableBuilder; + + // Create a index reader based on the index type stored in the table. + // Optionally, user can pass a preloaded meta_index_iter for the index that + // need to access extra meta blocks for index construction. This parameter + // helps avoid re-reading meta index block if caller already created one. + Status CreateIndexReader(FilePrefetchBuffer* prefetch_buffer, + InternalIterator* preloaded_meta_index_iter, + bool use_cache, bool prefetch, bool pin, + BlockCacheLookupContext* lookup_context, + std::unique_ptr<IndexReader>* index_reader); + + bool FullFilterKeyMayMatch(const ReadOptions& read_options, + FilterBlockReader* filter, const Slice& user_key, + const bool no_io, + const SliceTransform* prefix_extractor, + GetContext* get_context, + BlockCacheLookupContext* lookup_context) const; + + void FullFilterKeysMayMatch(const ReadOptions& read_options, + FilterBlockReader* filter, MultiGetRange* range, + const bool no_io, + const SliceTransform* prefix_extractor, + BlockCacheLookupContext* lookup_context) const; + + static Status PrefetchTail( + RandomAccessFileReader* file, uint64_t file_size, + TailPrefetchStats* tail_prefetch_stats, const bool prefetch_all, + const bool preload_all, + std::unique_ptr<FilePrefetchBuffer>* prefetch_buffer); + Status ReadMetaIndexBlock(FilePrefetchBuffer* prefetch_buffer, + std::unique_ptr<Block>* metaindex_block, + std::unique_ptr<InternalIterator>* iter); + Status TryReadPropertiesWithGlobalSeqno(FilePrefetchBuffer* prefetch_buffer, + const Slice& handle_value, + TableProperties** table_properties); + Status ReadPropertiesBlock(FilePrefetchBuffer* prefetch_buffer, + InternalIterator* meta_iter, + const SequenceNumber largest_seqno); + Status ReadRangeDelBlock(FilePrefetchBuffer* prefetch_buffer, + InternalIterator* meta_iter, + const InternalKeyComparator& internal_comparator, + BlockCacheLookupContext* lookup_context); + Status PrefetchIndexAndFilterBlocks( + FilePrefetchBuffer* prefetch_buffer, InternalIterator* meta_iter, + BlockBasedTable* new_table, bool prefetch_all, + const BlockBasedTableOptions& table_options, const int level, + BlockCacheLookupContext* lookup_context); + + static BlockType GetBlockTypeForMetaBlockByName(const Slice& meta_block_name); + + Status VerifyChecksumInMetaBlocks(InternalIteratorBase<Slice>* index_iter); + Status VerifyChecksumInBlocks(const ReadOptions& read_options, + InternalIteratorBase<IndexValue>* index_iter); + + // Create the filter from the filter block. + std::unique_ptr<FilterBlockReader> CreateFilterBlockReader( + FilePrefetchBuffer* prefetch_buffer, bool use_cache, bool prefetch, + bool pin, BlockCacheLookupContext* lookup_context); + + static void SetupCacheKeyPrefix(Rep* rep); + + // Generate a cache key prefix from the file + static void GenerateCachePrefix(Cache* cc, FSRandomAccessFile* file, + char* buffer, size_t* size); + static void GenerateCachePrefix(Cache* cc, FSWritableFile* file, char* buffer, + size_t* size); + + // Given an iterator return its offset in file. + uint64_t ApproximateOffsetOf( + const InternalIteratorBase<IndexValue>& index_iter) const; + + // Helper functions for DumpTable() + Status DumpIndexBlock(WritableFile* out_file); + Status DumpDataBlocks(WritableFile* out_file); + void DumpKeyValue(const Slice& key, const Slice& value, + WritableFile* out_file); + + // A cumulative data block file read in MultiGet lower than this size will + // use a stack buffer + static constexpr size_t kMultiGetReadStackBufSize = 8192; + + friend class PartitionedFilterBlockReader; + friend class PartitionedFilterBlockTest; + friend class DBBasicTest_MultiGetIOBufferOverrun_Test; +}; + +// Maitaning state of a two-level iteration on a partitioned index structure. +class BlockBasedTable::PartitionedIndexIteratorState + : public TwoLevelIteratorState { + public: + PartitionedIndexIteratorState( + const BlockBasedTable* table, + std::unordered_map<uint64_t, CachableEntry<Block>>* block_map); + InternalIteratorBase<IndexValue>* NewSecondaryIterator( + const BlockHandle& index_value) override; + + private: + // Don't own table_ + const BlockBasedTable* table_; + std::unordered_map<uint64_t, CachableEntry<Block>>* block_map_; +}; + +// Stores all the properties associated with a BlockBasedTable. +// These are immutable. +struct BlockBasedTable::Rep { + Rep(const ImmutableCFOptions& _ioptions, const EnvOptions& _env_options, + const BlockBasedTableOptions& _table_opt, + const InternalKeyComparator& _internal_comparator, bool skip_filters, + int _level, const bool _immortal_table) + : ioptions(_ioptions), + env_options(_env_options), + table_options(_table_opt), + filter_policy(skip_filters ? nullptr : _table_opt.filter_policy.get()), + internal_comparator(_internal_comparator), + filter_type(FilterType::kNoFilter), + index_type(BlockBasedTableOptions::IndexType::kBinarySearch), + hash_index_allow_collision(false), + whole_key_filtering(_table_opt.whole_key_filtering), + prefix_filtering(true), + global_seqno(kDisableGlobalSequenceNumber), + level(_level), + immortal_table(_immortal_table) {} + + const ImmutableCFOptions& ioptions; + const EnvOptions& env_options; + const BlockBasedTableOptions table_options; + const FilterPolicy* const filter_policy; + const InternalKeyComparator& internal_comparator; + Status status; + std::unique_ptr<RandomAccessFileReader> file; + char cache_key_prefix[kMaxCacheKeyPrefixSize]; + size_t cache_key_prefix_size = 0; + char persistent_cache_key_prefix[kMaxCacheKeyPrefixSize]; + size_t persistent_cache_key_prefix_size = 0; + char compressed_cache_key_prefix[kMaxCacheKeyPrefixSize]; + size_t compressed_cache_key_prefix_size = 0; + PersistentCacheOptions persistent_cache_options; + + // Footer contains the fixed table information + Footer footer; + + std::unique_ptr<IndexReader> index_reader; + std::unique_ptr<FilterBlockReader> filter; + std::unique_ptr<UncompressionDictReader> uncompression_dict_reader; + + enum class FilterType { + kNoFilter, + kFullFilter, + kBlockFilter, + kPartitionedFilter, + }; + FilterType filter_type; + BlockHandle filter_handle; + BlockHandle compression_dict_handle; + + std::shared_ptr<const TableProperties> table_properties; + BlockBasedTableOptions::IndexType index_type; + bool hash_index_allow_collision; + bool whole_key_filtering; + bool prefix_filtering; + // TODO(kailiu) It is very ugly to use internal key in table, since table + // module should not be relying on db module. However to make things easier + // and compatible with existing code, we introduce a wrapper that allows + // block to extract prefix without knowing if a key is internal or not. + // null if no prefix_extractor is passed in when opening the table reader. + std::unique_ptr<SliceTransform> internal_prefix_transform; + std::shared_ptr<const SliceTransform> table_prefix_extractor; + + std::shared_ptr<const FragmentedRangeTombstoneList> fragmented_range_dels; + + // If global_seqno is used, all Keys in this file will have the same + // seqno with value `global_seqno`. + // + // A value of kDisableGlobalSequenceNumber means that this feature is disabled + // and every key have it's own seqno. + SequenceNumber global_seqno; + + // the level when the table is opened, could potentially change when trivial + // move is involved + int level; + + // If false, blocks in this file are definitely all uncompressed. Knowing this + // before reading individual blocks enables certain optimizations. + bool blocks_maybe_compressed = true; + + // If true, data blocks in this file are definitely ZSTD compressed. If false + // they might not be. When false we skip creating a ZSTD digested + // uncompression dictionary. Even if we get a false negative, things should + // still work, just not as quickly. + bool blocks_definitely_zstd_compressed = false; + + // These describe how index is encoded. + bool index_has_first_key = false; + bool index_key_includes_seq = true; + bool index_value_is_full = true; + + const bool immortal_table; + + SequenceNumber get_global_seqno(BlockType block_type) const { + return (block_type == BlockType::kFilter || + block_type == BlockType::kCompressionDictionary) + ? kDisableGlobalSequenceNumber + : global_seqno; + } + + uint64_t cf_id_for_tracing() const { + return table_properties + ? table_properties->column_family_id + : ROCKSDB_NAMESPACE::TablePropertiesCollectorFactory::Context:: + kUnknownColumnFamily; + } + + Slice cf_name_for_tracing() const { + return table_properties ? table_properties->column_family_name + : BlockCacheTraceHelper::kUnknownColumnFamilyName; + } + + uint32_t level_for_tracing() const { return level >= 0 ? level : UINT32_MAX; } + + uint64_t sst_number_for_tracing() const { + return file ? TableFileNameToNumber(file->file_name()) : UINT64_MAX; + } + void CreateFilePrefetchBuffer( + size_t readahead_size, size_t max_readahead_size, + std::unique_ptr<FilePrefetchBuffer>* fpb) const { + fpb->reset(new FilePrefetchBuffer(file.get(), readahead_size, + max_readahead_size, + !ioptions.allow_mmap_reads /* enable */)); + } +}; + +// Iterates over the contents of BlockBasedTable. +template <class TBlockIter, typename TValue = Slice> +class BlockBasedTableIterator : public InternalIteratorBase<TValue> { + // compaction_readahead_size: its value will only be used if for_compaction = + // true + public: + BlockBasedTableIterator(const BlockBasedTable* table, + const ReadOptions& read_options, + const InternalKeyComparator& icomp, + InternalIteratorBase<IndexValue>* index_iter, + bool check_filter, bool need_upper_bound_check, + const SliceTransform* prefix_extractor, + BlockType block_type, TableReaderCaller caller, + size_t compaction_readahead_size = 0) + : table_(table), + read_options_(read_options), + icomp_(icomp), + user_comparator_(icomp.user_comparator()), + index_iter_(index_iter), + pinned_iters_mgr_(nullptr), + block_iter_points_to_real_block_(false), + check_filter_(check_filter), + need_upper_bound_check_(need_upper_bound_check), + prefix_extractor_(prefix_extractor), + block_type_(block_type), + lookup_context_(caller), + compaction_readahead_size_(compaction_readahead_size) {} + + ~BlockBasedTableIterator() { delete index_iter_; } + + void Seek(const Slice& target) override; + void SeekForPrev(const Slice& target) override; + void SeekToFirst() override; + void SeekToLast() override; + void Next() final override; + bool NextAndGetResult(IterateResult* result) override; + void Prev() override; + bool Valid() const override { + return !is_out_of_bound_ && + (is_at_first_key_from_index_ || + (block_iter_points_to_real_block_ && block_iter_.Valid())); + } + Slice key() const override { + assert(Valid()); + if (is_at_first_key_from_index_) { + return index_iter_->value().first_internal_key; + } else { + return block_iter_.key(); + } + } + Slice user_key() const override { + assert(Valid()); + if (is_at_first_key_from_index_) { + return ExtractUserKey(index_iter_->value().first_internal_key); + } else { + return block_iter_.user_key(); + } + } + TValue value() const override { + assert(Valid()); + + // Load current block if not loaded. + if (is_at_first_key_from_index_ && + !const_cast<BlockBasedTableIterator*>(this) + ->MaterializeCurrentBlock()) { + // Oops, index is not consistent with block contents, but we have + // no good way to report error at this point. Let's return empty value. + return TValue(); + } + + return block_iter_.value(); + } + Status status() const override { + // Prefix index set status to NotFound when the prefix does not exist + if (!index_iter_->status().ok() && !index_iter_->status().IsNotFound()) { + return index_iter_->status(); + } else if (block_iter_points_to_real_block_) { + return block_iter_.status(); + } else { + return Status::OK(); + } + } + + // Whether iterator invalidated for being out of bound. + bool IsOutOfBound() override { return is_out_of_bound_; } + + inline bool MayBeOutOfUpperBound() override { + assert(Valid()); + return !data_block_within_upper_bound_; + } + + void SetPinnedItersMgr(PinnedIteratorsManager* pinned_iters_mgr) override { + pinned_iters_mgr_ = pinned_iters_mgr; + } + bool IsKeyPinned() const override { + // Our key comes either from block_iter_'s current key + // or index_iter_'s current *value*. + return pinned_iters_mgr_ && pinned_iters_mgr_->PinningEnabled() && + ((is_at_first_key_from_index_ && index_iter_->IsValuePinned()) || + (block_iter_points_to_real_block_ && block_iter_.IsKeyPinned())); + } + bool IsValuePinned() const override { + // Load current block if not loaded. + if (is_at_first_key_from_index_) { + const_cast<BlockBasedTableIterator*>(this)->MaterializeCurrentBlock(); + } + // BlockIter::IsValuePinned() is always true. No need to check + return pinned_iters_mgr_ && pinned_iters_mgr_->PinningEnabled() && + block_iter_points_to_real_block_; + } + + void ResetDataIter() { + if (block_iter_points_to_real_block_) { + if (pinned_iters_mgr_ != nullptr && pinned_iters_mgr_->PinningEnabled()) { + block_iter_.DelegateCleanupsTo(pinned_iters_mgr_); + } + block_iter_.Invalidate(Status::OK()); + block_iter_points_to_real_block_ = false; + } + } + + void SavePrevIndexValue() { + if (block_iter_points_to_real_block_) { + // Reseek. If they end up with the same data block, we shouldn't re-fetch + // the same data block. + prev_block_offset_ = index_iter_->value().handle.offset(); + } + } + + private: + enum class IterDirection { + kForward, + kBackward, + }; + + const BlockBasedTable* table_; + const ReadOptions read_options_; + const InternalKeyComparator& icomp_; + UserComparatorWrapper user_comparator_; + InternalIteratorBase<IndexValue>* index_iter_; + PinnedIteratorsManager* pinned_iters_mgr_; + TBlockIter block_iter_; + + // True if block_iter_ is initialized and points to the same block + // as index iterator. + bool block_iter_points_to_real_block_; + // See InternalIteratorBase::IsOutOfBound(). + bool is_out_of_bound_ = false; + // Whether current data block being fully within iterate upper bound. + bool data_block_within_upper_bound_ = false; + // True if we're standing at the first key of a block, and we haven't loaded + // that block yet. A call to value() will trigger loading the block. + bool is_at_first_key_from_index_ = false; + bool check_filter_; + // TODO(Zhongyi): pick a better name + bool need_upper_bound_check_; + const SliceTransform* prefix_extractor_; + BlockType block_type_; + uint64_t prev_block_offset_ = std::numeric_limits<uint64_t>::max(); + BlockCacheLookupContext lookup_context_; + // Readahead size used in compaction, its value is used only if + // lookup_context_.caller = kCompaction. + size_t compaction_readahead_size_; + + size_t readahead_size_ = BlockBasedTable::kInitAutoReadaheadSize; + size_t readahead_limit_ = 0; + int64_t num_file_reads_ = 0; + std::unique_ptr<FilePrefetchBuffer> prefetch_buffer_; + + // If `target` is null, seek to first. + void SeekImpl(const Slice* target); + + void InitDataBlock(); + bool MaterializeCurrentBlock(); + void FindKeyForward(); + void FindBlockForward(); + void FindKeyBackward(); + void CheckOutOfBound(); + + // Check if data block is fully within iterate_upper_bound. + // + // Note MyRocks may update iterate bounds between seek. To workaround it, + // we need to check and update data_block_within_upper_bound_ accordingly. + void CheckDataBlockWithinUpperBound(); + + bool CheckPrefixMayMatch(const Slice& ikey, IterDirection direction) { + if (need_upper_bound_check_ && direction == IterDirection::kBackward) { + // Upper bound check isn't sufficnet for backward direction to + // guarantee the same result as total order, so disable prefix + // check. + return true; + } + if (check_filter_ && + !table_->PrefixMayMatch(ikey, read_options_, prefix_extractor_, + need_upper_bound_check_, &lookup_context_)) { + // TODO remember the iterator is invalidated because of prefix + // match. This can avoid the upper level file iterator to falsely + // believe the position is the end of the SST file and move to + // the first key of the next file. + ResetDataIter(); + return false; + } + return true; + } +}; + +} // namespace ROCKSDB_NAMESPACE |