// Copyright (c) 2013, Facebook, Inc. All rights reserved. // This source code is licensed under the BSD-style license found in the // LICENSE file in the root directory of this source tree. An additional grant // of patent rights can be found in the PATENTS file in the same 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. #include "table/block_based_table_reader.h" #include #include #include "db/dbformat.h" #include "rocksdb/cache.h" #include "rocksdb/comparator.h" #include "rocksdb/env.h" #include "rocksdb/filter_policy.h" #include "rocksdb/iterator.h" #include "rocksdb/options.h" #include "rocksdb/statistics.h" #include "rocksdb/table.h" #include "rocksdb/table_properties.h" #include "table/block.h" #include "table/filter_block.h" #include "table/block_based_filter_block.h" #include "table/full_filter_block.h" #include "table/block_hash_index.h" #include "table/block_prefix_index.h" #include "table/format.h" #include "table/meta_blocks.h" #include "table/two_level_iterator.h" #include "table/get_context.h" #include "util/coding.h" #include "util/perf_context_imp.h" #include "util/stop_watch.h" #include "util/string_util.h" namespace rocksdb { extern const uint64_t kBlockBasedTableMagicNumber; extern const std::string kHashIndexPrefixesBlock; extern const std::string kHashIndexPrefixesMetadataBlock; using std::unique_ptr; typedef BlockBasedTable::IndexReader IndexReader; namespace { // The longest the prefix of the cache key used to identify blocks can be. // We are using the fact that we know for Posix files the unique ID is three // varints. // For some reason, compiling for iOS complains that this variable is unused const size_t kMaxCacheKeyPrefixSize __attribute__((unused)) = kMaxVarint64Length * 3 + 1; // Read the block identified by "handle" from "file". // The only relevant option is options.verify_checksums for now. // On failure return non-OK. // On success fill *result and return OK - caller owns *result Status ReadBlockFromFile(RandomAccessFile* file, const Footer& footer, const ReadOptions& options, const BlockHandle& handle, Block** result, Env* env, bool do_uncompress = true) { BlockContents contents; Status s = ReadBlockContents(file, footer, options, handle, &contents, env, do_uncompress); if (s.ok()) { *result = new Block(std::move(contents)); } return s; } // Delete the resource that is held by the iterator. template void DeleteHeldResource(void* arg, void* ignored) { delete reinterpret_cast(arg); } // Delete the entry resided in the cache. template void DeleteCachedEntry(const Slice& key, void* value) { auto entry = reinterpret_cast(value); delete entry; } // Release the cached entry and decrement its ref count. void ReleaseCachedEntry(void* arg, void* h) { Cache* cache = reinterpret_cast(arg); Cache::Handle* handle = reinterpret_cast(h); cache->Release(handle); } Slice GetCacheKey(const char* cache_key_prefix, size_t cache_key_prefix_size, const BlockHandle& handle, char* cache_key) { assert(cache_key != nullptr); assert(cache_key_prefix_size != 0); assert(cache_key_prefix_size <= kMaxCacheKeyPrefixSize); memcpy(cache_key, cache_key_prefix, cache_key_prefix_size); char* end = EncodeVarint64(cache_key + cache_key_prefix_size, handle.offset()); return Slice(cache_key, static_cast(end - cache_key)); } Cache::Handle* GetEntryFromCache(Cache* block_cache, const Slice& key, Tickers block_cache_miss_ticker, Tickers block_cache_hit_ticker, Statistics* statistics) { auto cache_handle = block_cache->Lookup(key); if (cache_handle != nullptr) { PERF_COUNTER_ADD(block_cache_hit_count, 1); // overall cache hit RecordTick(statistics, BLOCK_CACHE_HIT); // block-type specific cache hit RecordTick(statistics, block_cache_hit_ticker); } else { // overall cache miss RecordTick(statistics, BLOCK_CACHE_MISS); // block-type specific cache miss RecordTick(statistics, block_cache_miss_ticker); } return cache_handle; } } // namespace // -- IndexReader and its subclasses // IndexReader is the interface that provide the functionality for index access. class BlockBasedTable::IndexReader { public: explicit IndexReader(const Comparator* comparator) : comparator_(comparator) {} virtual ~IndexReader() {} // Create an iterator for index access. // An iter is passed in, if it is not null, update this one and return it // If it is null, create a new Iterator virtual Iterator* NewIterator( BlockIter* iter = nullptr, bool total_order_seek = true) = 0; // The size of the index. virtual size_t size() const = 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; protected: const Comparator* comparator_; }; // Index that allows binary search lookup for the first key of each block. // This class can be viewed as a thin wrapper for `Block` class which already // supports binary search. class BinarySearchIndexReader : public IndexReader { public: // Read index from the file and create an intance for // `BinarySearchIndexReader`. // On success, index_reader will be populated; otherwise it will remain // unmodified. static Status Create(RandomAccessFile* file, const Footer& footer, const BlockHandle& index_handle, Env* env, const Comparator* comparator, IndexReader** index_reader) { Block* index_block = nullptr; auto s = ReadBlockFromFile(file, footer, ReadOptions(), index_handle, &index_block, env); if (s.ok()) { *index_reader = new BinarySearchIndexReader(comparator, index_block); } return s; } virtual Iterator* NewIterator( BlockIter* iter = nullptr, bool dont_care = true) override { return index_block_->NewIterator(comparator_, iter, true); } virtual size_t size() const override { return index_block_->size(); } virtual size_t ApproximateMemoryUsage() const override { assert(index_block_); return index_block_->ApproximateMemoryUsage(); } private: BinarySearchIndexReader(const Comparator* comparator, Block* index_block) : IndexReader(comparator), index_block_(index_block) { assert(index_block_ != nullptr); } std::unique_ptr index_block_; }; // Index that leverages an internal hash table to quicken the lookup for a given // key. class HashIndexReader : public IndexReader { public: static Status Create(const SliceTransform* hash_key_extractor, const Footer& footer, RandomAccessFile* file, Env* env, const Comparator* comparator, const BlockHandle& index_handle, Iterator* meta_index_iter, IndexReader** index_reader, bool hash_index_allow_collision) { Block* index_block = nullptr; auto s = ReadBlockFromFile(file, footer, ReadOptions(), index_handle, &index_block, env); if (!s.ok()) { return s; } // Note, failure to create prefix hash index does not need to be a // hard error. We can still fall back to the original binary search index. // So, Create will succeed regardless, from this point on. auto new_index_reader = new HashIndexReader(comparator, index_block); *index_reader = new_index_reader; // Get prefixes block BlockHandle prefixes_handle; s = FindMetaBlock(meta_index_iter, kHashIndexPrefixesBlock, &prefixes_handle); if (!s.ok()) { // TODO: log error return Status::OK(); } // Get index metadata block BlockHandle prefixes_meta_handle; s = FindMetaBlock(meta_index_iter, kHashIndexPrefixesMetadataBlock, &prefixes_meta_handle); if (!s.ok()) { // TODO: log error return Status::OK(); } // Read contents for the blocks BlockContents prefixes_contents; s = ReadBlockContents(file, footer, ReadOptions(), prefixes_handle, &prefixes_contents, env, true /* do decompression */); if (!s.ok()) { return s; } BlockContents prefixes_meta_contents; s = ReadBlockContents(file, footer, ReadOptions(), prefixes_meta_handle, &prefixes_meta_contents, env, true /* do decompression */); if (!s.ok()) { // TODO: log error return Status::OK(); } if (!hash_index_allow_collision) { // TODO: deprecate once hash_index_allow_collision proves to be stable. BlockHashIndex* hash_index = nullptr; s = CreateBlockHashIndex(hash_key_extractor, prefixes_contents.data, prefixes_meta_contents.data, &hash_index); // TODO: log error if (s.ok()) { new_index_reader->index_block_->SetBlockHashIndex(hash_index); new_index_reader->OwnPrefixesContents(std::move(prefixes_contents)); } } else { BlockPrefixIndex* prefix_index = nullptr; s = BlockPrefixIndex::Create(hash_key_extractor, prefixes_contents.data, prefixes_meta_contents.data, &prefix_index); // TODO: log error if (s.ok()) { new_index_reader->index_block_->SetBlockPrefixIndex(prefix_index); } } return Status::OK(); } virtual Iterator* NewIterator( BlockIter* iter = nullptr, bool total_order_seek = true) override { return index_block_->NewIterator(comparator_, iter, total_order_seek); } virtual size_t size() const override { return index_block_->size(); } virtual size_t ApproximateMemoryUsage() const override { assert(index_block_); return index_block_->ApproximateMemoryUsage() + prefixes_contents_.data.size(); } private: HashIndexReader(const Comparator* comparator, Block* index_block) : IndexReader(comparator), index_block_(index_block) { assert(index_block_ != nullptr); } ~HashIndexReader() { } void OwnPrefixesContents(BlockContents&& prefixes_contents) { prefixes_contents_ = std::move(prefixes_contents); } std::unique_ptr index_block_; BlockContents prefixes_contents_; }; struct BlockBasedTable::Rep { Rep(const ImmutableCFOptions& _ioptions, const EnvOptions& _env_options, const BlockBasedTableOptions& _table_opt, const InternalKeyComparator& _internal_comparator) : ioptions(_ioptions), env_options(_env_options), table_options(_table_opt), filter_policy(_table_opt.filter_policy.get()), internal_comparator(_internal_comparator) {} const ImmutableCFOptions& ioptions; const EnvOptions& env_options; const BlockBasedTableOptions& table_options; const FilterPolicy* const filter_policy; const InternalKeyComparator& internal_comparator; Status status; unique_ptr file; char cache_key_prefix[kMaxCacheKeyPrefixSize]; size_t cache_key_prefix_size = 0; char compressed_cache_key_prefix[kMaxCacheKeyPrefixSize]; size_t compressed_cache_key_prefix_size = 0; // Footer contains the fixed table information Footer footer; // index_reader and filter will be populated and used only when // options.block_cache is nullptr; otherwise we will get the index block via // the block cache. unique_ptr index_reader; unique_ptr filter; std::shared_ptr table_properties; BlockBasedTableOptions::IndexType index_type; bool hash_index_allow_collision; // 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. unique_ptr internal_prefix_transform; }; BlockBasedTable::~BlockBasedTable() { delete rep_; } // CachableEntry represents the entries that *may* be fetched from block cache. // field `value` is the item we want to get. // field `cache_handle` is the cache handle to the block cache. If the value // was not read from cache, `cache_handle` will be nullptr. template struct BlockBasedTable::CachableEntry { CachableEntry(TValue* _value, Cache::Handle* _cache_handle) : value(_value), cache_handle(_cache_handle) {} CachableEntry() : CachableEntry(nullptr, nullptr) {} void Release(Cache* cache) { if (cache_handle) { cache->Release(cache_handle); value = nullptr; cache_handle = nullptr; } } TValue* value = nullptr; // if the entry is from the cache, cache_handle will be populated. Cache::Handle* cache_handle = nullptr; }; // Helper function to setup the cache key's prefix for the Table. void BlockBasedTable::SetupCacheKeyPrefix(Rep* rep) { assert(kMaxCacheKeyPrefixSize >= 10); rep->cache_key_prefix_size = 0; rep->compressed_cache_key_prefix_size = 0; if (rep->table_options.block_cache != nullptr) { GenerateCachePrefix(rep->table_options.block_cache.get(), rep->file.get(), &rep->cache_key_prefix[0], &rep->cache_key_prefix_size); } if (rep->table_options.block_cache_compressed != nullptr) { GenerateCachePrefix(rep->table_options.block_cache_compressed.get(), rep->file.get(), &rep->compressed_cache_key_prefix[0], &rep->compressed_cache_key_prefix_size); } } void BlockBasedTable::GenerateCachePrefix(Cache* cc, RandomAccessFile* file, char* buffer, size_t* size) { // generate an id from the file *size = file->GetUniqueId(buffer, kMaxCacheKeyPrefixSize); // If the prefix wasn't generated or was too long, // create one from the cache. if (*size == 0) { char* end = EncodeVarint64(buffer, cc->NewId()); *size = static_cast(end - buffer); } } void BlockBasedTable::GenerateCachePrefix(Cache* cc, WritableFile* file, char* buffer, size_t* size) { // generate an id from the file *size = file->GetUniqueId(buffer, kMaxCacheKeyPrefixSize); // If the prefix wasn't generated or was too long, // create one from the cache. if (*size == 0) { char* end = EncodeVarint64(buffer, cc->NewId()); *size = static_cast(end - buffer); } } Status BlockBasedTable::Open(const ImmutableCFOptions& ioptions, const EnvOptions& env_options, const BlockBasedTableOptions& table_options, const InternalKeyComparator& internal_comparator, unique_ptr&& file, uint64_t file_size, unique_ptr* table_reader) { table_reader->reset(); Footer footer; auto s = ReadFooterFromFile(file.get(), file_size, &footer, kBlockBasedTableMagicNumber); if (!s.ok()) { return s; } if (!BlockBasedTableSupportedVersion(footer.version())) { return Status::Corruption( "Unknown Footer version. Maybe this file was created with newer " "version of RocksDB?"); } // We've successfully read the footer and the index block: we're // ready to serve requests. Rep* rep = new BlockBasedTable::Rep( ioptions, env_options, table_options, internal_comparator); rep->file = std::move(file); rep->footer = footer; rep->index_type = table_options.index_type; rep->hash_index_allow_collision = table_options.hash_index_allow_collision; SetupCacheKeyPrefix(rep); unique_ptr new_table(new BlockBasedTable(rep)); // Read meta index std::unique_ptr meta; std::unique_ptr meta_iter; s = ReadMetaBlock(rep, &meta, &meta_iter); if (!s.ok()) { return s; } // Read the properties bool found_properties_block = true; s = SeekToPropertiesBlock(meta_iter.get(), &found_properties_block); if (!s.ok()) { Log(InfoLogLevel::WARN_LEVEL, rep->ioptions.info_log, "Cannot seek to properties block from file: %s", s.ToString().c_str()); } else if (found_properties_block) { s = meta_iter->status(); TableProperties* table_properties = nullptr; if (s.ok()) { s = ReadProperties(meta_iter->value(), rep->file.get(), rep->footer, rep->ioptions.env, rep->ioptions.info_log, &table_properties); } if (!s.ok()) { Log(InfoLogLevel::WARN_LEVEL, rep->ioptions.info_log, "Encountered error while reading data from properties " "block %s", s.ToString().c_str()); } else { rep->table_properties.reset(table_properties); } } else { Log(InfoLogLevel::ERROR_LEVEL, rep->ioptions.info_log, "Cannot find Properties block from file."); } // Will use block cache for index/filter blocks access? if (table_options.cache_index_and_filter_blocks) { assert(table_options.block_cache != nullptr); // Hack: Call NewIndexIterator() to implicitly add index to the block_cache unique_ptr iter(new_table->NewIndexIterator(ReadOptions())); s = iter->status(); if (s.ok()) { // Hack: Call GetFilter() to implicitly add filter to the block_cache auto filter_entry = new_table->GetFilter(); filter_entry.Release(table_options.block_cache.get()); } } else { // If we don't use block cache for index/filter blocks access, we'll // pre-load these blocks, which will kept in member variables in Rep // and with a same life-time as this table object. IndexReader* index_reader = nullptr; s = new_table->CreateIndexReader(&index_reader, meta_iter.get()); if (s.ok()) { rep->index_reader.reset(index_reader); // Set filter block if (rep->filter_policy) { rep->filter.reset(ReadFilter(rep, meta_iter.get(), nullptr)); } } else { delete index_reader; } } if (s.ok()) { *table_reader = std::move(new_table); } return s; } void BlockBasedTable::SetupForCompaction() { switch (rep_->ioptions.access_hint_on_compaction_start) { case Options::NONE: break; case Options::NORMAL: rep_->file->Hint(RandomAccessFile::NORMAL); break; case Options::SEQUENTIAL: rep_->file->Hint(RandomAccessFile::SEQUENTIAL); break; case Options::WILLNEED: rep_->file->Hint(RandomAccessFile::WILLNEED); break; default: assert(false); } compaction_optimized_ = true; } std::shared_ptr BlockBasedTable::GetTableProperties() const { return rep_->table_properties; } size_t BlockBasedTable::ApproximateMemoryUsage() const { size_t usage = 0; if (rep_->filter) { usage += rep_->filter->ApproximateMemoryUsage(); } if (rep_->index_reader) { usage += rep_->index_reader->ApproximateMemoryUsage(); } return usage; } // Load the meta-block from the file. On success, return the loaded meta block // and its iterator. Status BlockBasedTable::ReadMetaBlock( Rep* rep, std::unique_ptr* meta_block, std::unique_ptr* iter) { // TODO(sanjay): Skip this if footer.metaindex_handle() size indicates // it is an empty block. // TODO: we never really verify check sum for meta index block Block* meta = nullptr; Status s = ReadBlockFromFile( rep->file.get(), rep->footer, ReadOptions(), rep->footer.metaindex_handle(), &meta, rep->ioptions.env); if (!s.ok()) { Log(InfoLogLevel::ERROR_LEVEL, rep->ioptions.info_log, "Encountered error while reading data from properties" " block %s", s.ToString().c_str()); delete meta; return s; } meta_block->reset(meta); // meta block uses bytewise comparator. iter->reset(meta->NewIterator(BytewiseComparator())); return Status::OK(); } Status BlockBasedTable::GetDataBlockFromCache( const Slice& block_cache_key, const Slice& compressed_block_cache_key, Cache* block_cache, Cache* block_cache_compressed, Statistics* statistics, const ReadOptions& read_options, BlockBasedTable::CachableEntry* block, uint32_t format_version) { Status s; Block* compressed_block = nullptr; Cache::Handle* block_cache_compressed_handle = nullptr; // Lookup uncompressed cache first if (block_cache != nullptr) { block->cache_handle = GetEntryFromCache(block_cache, block_cache_key, BLOCK_CACHE_DATA_MISS, BLOCK_CACHE_DATA_HIT, statistics); if (block->cache_handle != nullptr) { block->value = reinterpret_cast(block_cache->Value(block->cache_handle)); return s; } } // If not found, search from the compressed block cache. assert(block->cache_handle == nullptr && block->value == nullptr); if (block_cache_compressed == nullptr) { return s; } assert(!compressed_block_cache_key.empty()); block_cache_compressed_handle = block_cache_compressed->Lookup(compressed_block_cache_key); // if we found in the compressed cache, then uncompress and insert into // uncompressed cache if (block_cache_compressed_handle == nullptr) { RecordTick(statistics, BLOCK_CACHE_COMPRESSED_MISS); return s; } // found compressed block RecordTick(statistics, BLOCK_CACHE_COMPRESSED_HIT); compressed_block = reinterpret_cast( block_cache_compressed->Value(block_cache_compressed_handle)); assert(compressed_block->compression_type() != kNoCompression); // Retrieve the uncompressed contents into a new buffer BlockContents contents; s = UncompressBlockContents(compressed_block->data(), compressed_block->size(), &contents, format_version); // Insert uncompressed block into block cache if (s.ok()) { block->value = new Block(std::move(contents)); // uncompressed block assert(block->value->compression_type() == kNoCompression); if (block_cache != nullptr && block->value->cachable() && read_options.fill_cache) { block->cache_handle = block_cache->Insert(block_cache_key, block->value, block->value->size(), &DeleteCachedEntry); assert(reinterpret_cast( block_cache->Value(block->cache_handle)) == block->value); } } // Release hold on compressed cache entry block_cache_compressed->Release(block_cache_compressed_handle); return s; } Status BlockBasedTable::PutDataBlockToCache( const Slice& block_cache_key, const Slice& compressed_block_cache_key, Cache* block_cache, Cache* block_cache_compressed, const ReadOptions& read_options, Statistics* statistics, CachableEntry* block, Block* raw_block, uint32_t format_version) { assert(raw_block->compression_type() == kNoCompression || block_cache_compressed != nullptr); Status s; // Retrieve the uncompressed contents into a new buffer BlockContents contents; if (raw_block->compression_type() != kNoCompression) { s = UncompressBlockContents(raw_block->data(), raw_block->size(), &contents, format_version); } if (!s.ok()) { delete raw_block; return s; } if (raw_block->compression_type() != kNoCompression) { block->value = new Block(std::move(contents)); // uncompressed block } else { block->value = raw_block; raw_block = nullptr; } // Insert compressed block into compressed block cache. // Release the hold on the compressed cache entry immediately. if (block_cache_compressed != nullptr && raw_block != nullptr && raw_block->cachable()) { auto cache_handle = block_cache_compressed->Insert( compressed_block_cache_key, raw_block, raw_block->size(), &DeleteCachedEntry); block_cache_compressed->Release(cache_handle); RecordTick(statistics, BLOCK_CACHE_COMPRESSED_MISS); // Avoid the following code to delete this cached block. raw_block = nullptr; } delete raw_block; // insert into uncompressed block cache assert((block->value->compression_type() == kNoCompression)); if (block_cache != nullptr && block->value->cachable()) { block->cache_handle = block_cache->Insert(block_cache_key, block->value, block->value->size(), &DeleteCachedEntry); RecordTick(statistics, BLOCK_CACHE_ADD); assert(reinterpret_cast(block_cache->Value(block->cache_handle)) == block->value); } return s; } FilterBlockReader* BlockBasedTable::ReadFilter( Rep* rep, Iterator* meta_index_iter, size_t* filter_size) { // TODO: We might want to unify with ReadBlockFromFile() if we start // requiring checksum verification in Table::Open. for (auto prefix : {kFullFilterBlockPrefix, kFilterBlockPrefix}) { std::string filter_block_key = prefix; filter_block_key.append(rep->filter_policy->Name()); BlockHandle handle; if (FindMetaBlock(meta_index_iter, filter_block_key, &handle).ok()) { BlockContents block; if (!ReadBlockContents(rep->file.get(), rep->footer, ReadOptions(), handle, &block, rep->ioptions.env, false).ok()) { // Error reading the block return nullptr; } if (filter_size) { *filter_size = block.data.size(); } assert(rep->filter_policy); if (kFilterBlockPrefix == prefix) { return new BlockBasedFilterBlockReader( rep->ioptions.prefix_extractor, rep->table_options, std::move(block)); } else if (kFullFilterBlockPrefix == prefix) { auto filter_bits_reader = rep->filter_policy-> GetFilterBitsReader(block.data); if (filter_bits_reader != nullptr) { return new FullFilterBlockReader(rep->ioptions.prefix_extractor, rep->table_options, std::move(block), filter_bits_reader); } } else { assert(false); return nullptr; } } } return nullptr; } BlockBasedTable::CachableEntry BlockBasedTable::GetFilter( bool no_io) const { // If cache_index_and_filter_blocks is false, filter should be pre-populated. // We will return rep_->filter anyway. rep_->filter can be nullptr if filter // read fails at Open() time. We don't want to reload again since it will // most probably fail again. if (!rep_->table_options.cache_index_and_filter_blocks) { return {rep_->filter.get(), nullptr /* cache handle */}; } Cache* block_cache = rep_->table_options.block_cache.get(); if (rep_->filter_policy == nullptr /* do not use filter */ || block_cache == nullptr /* no block cache at all */) { return {nullptr /* filter */, nullptr /* cache handle */}; } // Fetching from the cache char cache_key[kMaxCacheKeyPrefixSize + kMaxVarint64Length]; auto key = GetCacheKey(rep_->cache_key_prefix, rep_->cache_key_prefix_size, rep_->footer.metaindex_handle(), cache_key); Statistics* statistics = rep_->ioptions.statistics; auto cache_handle = GetEntryFromCache(block_cache, key, BLOCK_CACHE_FILTER_MISS, BLOCK_CACHE_FILTER_HIT, statistics); FilterBlockReader* filter = nullptr; if (cache_handle != nullptr) { filter = reinterpret_cast( block_cache->Value(cache_handle)); } else if (no_io) { // Do not invoke any io. return CachableEntry(); } else { size_t filter_size = 0; std::unique_ptr meta; std::unique_ptr iter; auto s = ReadMetaBlock(rep_, &meta, &iter); if (s.ok()) { filter = ReadFilter(rep_, iter.get(), &filter_size); if (filter != nullptr) { assert(filter_size > 0); cache_handle = block_cache->Insert( key, filter, filter_size, &DeleteCachedEntry); RecordTick(statistics, BLOCK_CACHE_ADD); } } } return { filter, cache_handle }; } Iterator* BlockBasedTable::NewIndexIterator(const ReadOptions& read_options, BlockIter* input_iter) { // index reader has already been pre-populated. if (rep_->index_reader) { return rep_->index_reader->NewIterator( input_iter, read_options.total_order_seek); } bool no_io = read_options.read_tier == kBlockCacheTier; Cache* block_cache = rep_->table_options.block_cache.get(); char cache_key[kMaxCacheKeyPrefixSize + kMaxVarint64Length]; auto key = GetCacheKey(rep_->cache_key_prefix, rep_->cache_key_prefix_size, rep_->footer.index_handle(), cache_key); Statistics* statistics = rep_->ioptions.statistics; auto cache_handle = GetEntryFromCache(block_cache, key, BLOCK_CACHE_INDEX_MISS, BLOCK_CACHE_INDEX_HIT, statistics); if (cache_handle == nullptr && no_io) { if (input_iter != nullptr) { input_iter->SetStatus(Status::Incomplete("no blocking io")); return input_iter; } else { return NewErrorIterator(Status::Incomplete("no blocking io")); } } IndexReader* index_reader = nullptr; if (cache_handle != nullptr) { index_reader = reinterpret_cast(block_cache->Value(cache_handle)); } else { // Create index reader and put it in the cache. Status s; s = CreateIndexReader(&index_reader); if (!s.ok()) { // make sure if something goes wrong, index_reader shall remain intact. assert(index_reader == nullptr); if (input_iter != nullptr) { input_iter->SetStatus(s); return input_iter; } else { return NewErrorIterator(s); } } cache_handle = block_cache->Insert(key, index_reader, index_reader->size(), &DeleteCachedEntry); RecordTick(statistics, BLOCK_CACHE_ADD); } assert(cache_handle); auto* iter = index_reader->NewIterator( input_iter, read_options.total_order_seek); iter->RegisterCleanup(&ReleaseCachedEntry, block_cache, cache_handle); return iter; } // Convert an index iterator value (i.e., an encoded BlockHandle) // into an iterator over the contents of the corresponding block. // If input_iter is null, new a iterator // If input_iter is not null, update this iter and return it Iterator* BlockBasedTable::NewDataBlockIterator(Rep* rep, const ReadOptions& ro, const Slice& index_value, BlockIter* input_iter) { const bool no_io = (ro.read_tier == kBlockCacheTier); Cache* block_cache = rep->table_options.block_cache.get(); Cache* block_cache_compressed = rep->table_options.block_cache_compressed.get(); CachableEntry block; BlockHandle handle; Slice input = index_value; // We intentionally allow extra stuff in index_value so that we // can add more features in the future. Status s = handle.DecodeFrom(&input); if (!s.ok()) { if (input_iter != nullptr) { input_iter->SetStatus(s); return input_iter; } else { return NewErrorIterator(s); } } // If either block cache is enabled, we'll try to read from it. if (block_cache != nullptr || block_cache_compressed != nullptr) { Statistics* statistics = rep->ioptions.statistics; char cache_key[kMaxCacheKeyPrefixSize + kMaxVarint64Length]; char compressed_cache_key[kMaxCacheKeyPrefixSize + kMaxVarint64Length]; Slice key, /* key to the block cache */ ckey /* key to the compressed block cache */; // create key for block cache if (block_cache != nullptr) { key = GetCacheKey(rep->cache_key_prefix, rep->cache_key_prefix_size, handle, cache_key); } if (block_cache_compressed != nullptr) { ckey = GetCacheKey(rep->compressed_cache_key_prefix, rep->compressed_cache_key_prefix_size, handle, compressed_cache_key); } s = GetDataBlockFromCache(key, ckey, block_cache, block_cache_compressed, statistics, ro, &block, rep->table_options.format_version); if (block.value == nullptr && !no_io && ro.fill_cache) { Block* raw_block = nullptr; { StopWatch sw(rep->ioptions.env, statistics, READ_BLOCK_GET_MICROS); s = ReadBlockFromFile(rep->file.get(), rep->footer, ro, handle, &raw_block, rep->ioptions.env, block_cache_compressed == nullptr); } if (s.ok()) { s = PutDataBlockToCache(key, ckey, block_cache, block_cache_compressed, ro, statistics, &block, raw_block, rep->table_options.format_version); } } } // Didn't get any data from block caches. if (block.value == nullptr) { if (no_io) { // Could not read from block_cache and can't do IO if (input_iter != nullptr) { input_iter->SetStatus(Status::Incomplete("no blocking io")); return input_iter; } else { return NewErrorIterator(Status::Incomplete("no blocking io")); } } s = ReadBlockFromFile(rep->file.get(), rep->footer, ro, handle, &block.value, rep->ioptions.env); } Iterator* iter; if (block.value != nullptr) { iter = block.value->NewIterator(&rep->internal_comparator, input_iter); if (block.cache_handle != nullptr) { iter->RegisterCleanup(&ReleaseCachedEntry, block_cache, block.cache_handle); } else { iter->RegisterCleanup(&DeleteHeldResource, block.value, nullptr); } } else { if (input_iter != nullptr) { input_iter->SetStatus(s); iter = input_iter; } else { iter = NewErrorIterator(s); } } return iter; } class BlockBasedTable::BlockEntryIteratorState : public TwoLevelIteratorState { public: BlockEntryIteratorState(BlockBasedTable* table, const ReadOptions& read_options) : TwoLevelIteratorState( table->rep_->ioptions.prefix_extractor != nullptr), table_(table), read_options_(read_options) {} Iterator* NewSecondaryIterator(const Slice& index_value) override { return NewDataBlockIterator(table_->rep_, read_options_, index_value); } bool PrefixMayMatch(const Slice& internal_key) override { if (read_options_.total_order_seek) { return true; } return table_->PrefixMayMatch(internal_key); } private: // Don't own table_ BlockBasedTable* table_; const ReadOptions read_options_; }; // This will be broken if the user specifies an unusual implementation // of Options.comparator, or if the user specifies an unusual // definition of prefixes in BlockBasedTableOptions.filter_policy. // In particular, we require the following three properties: // // 1) key.starts_with(prefix(key)) // 2) Compare(prefix(key), key) <= 0. // 3) If Compare(key1, key2) <= 0, then Compare(prefix(key1), prefix(key2)) <= 0 // // Otherwise, this method guarantees no I/O will be incurred. // // REQUIRES: this method shouldn't be called while the DB lock is held. bool BlockBasedTable::PrefixMayMatch(const Slice& internal_key) { if (!rep_->filter_policy) { return true; } assert(rep_->ioptions.prefix_extractor != nullptr); auto prefix = rep_->ioptions.prefix_extractor->Transform( ExtractUserKey(internal_key)); InternalKey internal_key_prefix(prefix, 0, kTypeValue); auto internal_prefix = internal_key_prefix.Encode(); bool may_match = true; Status s; // To prevent any io operation in this method, we set `read_tier` to make // sure we always read index or filter only when they have already been // loaded to memory. ReadOptions no_io_read_options; no_io_read_options.read_tier = kBlockCacheTier; // First, try check with full filter auto filter_entry = GetFilter(true /* no io */); FilterBlockReader* filter = filter_entry.value; if (filter != nullptr && !filter->IsBlockBased()) { may_match = filter->PrefixMayMatch(prefix); } // Then, try find it within each block if (may_match) { unique_ptr iiter(NewIndexIterator(no_io_read_options)); iiter->Seek(internal_prefix); if (!iiter->Valid()) { // we're past end of file // if it's incomplete, it means that we avoided I/O // and we're not really sure that we're past the end // of the file may_match = iiter->status().IsIncomplete(); } else if (ExtractUserKey(iiter->key()).starts_with( ExtractUserKey(internal_prefix))) { // we need to check for this subtle case because our only // guarantee is that "the key is a string >= last key in that data // block" according to the doc/table_format.txt spec. // // Suppose iiter->key() starts with the desired prefix; it is not // necessarily the case that the corresponding data block will // contain the prefix, since iiter->key() need not be in the // block. However, the next data block may contain the prefix, so // we return true to play it safe. may_match = true; } else if (filter != nullptr && filter->IsBlockBased()) { // iiter->key() does NOT start with the desired prefix. Because // Seek() finds the first key that is >= the seek target, this // means that iiter->key() > prefix. Thus, any data blocks coming // after the data block corresponding to iiter->key() cannot // possibly contain the key. Thus, the corresponding data block // is the only on could potentially contain the prefix. Slice handle_value = iiter->value(); BlockHandle handle; s = handle.DecodeFrom(&handle_value); assert(s.ok()); may_match = filter->PrefixMayMatch(prefix, handle.offset()); } } Statistics* statistics = rep_->ioptions.statistics; RecordTick(statistics, BLOOM_FILTER_PREFIX_CHECKED); if (!may_match) { RecordTick(statistics, BLOOM_FILTER_PREFIX_USEFUL); } filter_entry.Release(rep_->table_options.block_cache.get()); return may_match; } Iterator* BlockBasedTable::NewIterator(const ReadOptions& read_options, Arena* arena) { return NewTwoLevelIterator(new BlockEntryIteratorState(this, read_options), NewIndexIterator(read_options), arena); } bool BlockBasedTable::FullFilterKeyMayMatch(FilterBlockReader* filter, const Slice& internal_key) const { if (filter == nullptr || filter->IsBlockBased()) { return true; } Slice user_key = ExtractUserKey(internal_key); if (!filter->KeyMayMatch(user_key)) { return false; } if (rep_->ioptions.prefix_extractor && !filter->PrefixMayMatch( rep_->ioptions.prefix_extractor->Transform(user_key))) { return false; } return true; } Status BlockBasedTable::Get( const ReadOptions& read_options, const Slice& key, GetContext* get_context) { Status s; auto filter_entry = GetFilter(read_options.read_tier == kBlockCacheTier); FilterBlockReader* filter = filter_entry.value; // First check the full filter // If full filter not useful, Then go into each block if (!FullFilterKeyMayMatch(filter, key)) { RecordTick(rep_->ioptions.statistics, BLOOM_FILTER_USEFUL); } else { BlockIter iiter; NewIndexIterator(read_options, &iiter); bool done = false; for (iiter.Seek(key); iiter.Valid() && !done; iiter.Next()) { Slice handle_value = iiter.value(); BlockHandle handle; bool not_exist_in_filter = filter != nullptr && filter->IsBlockBased() == true && handle.DecodeFrom(&handle_value).ok() && !filter->KeyMayMatch(ExtractUserKey(key), handle.offset()); if (not_exist_in_filter) { // Not found // TODO: think about interaction with Merge. If a user key cannot // cross one data block, we should be fine. RecordTick(rep_->ioptions.statistics, BLOOM_FILTER_USEFUL); break; } else { BlockIter biter; NewDataBlockIterator(rep_, read_options, iiter.value(), &biter); if (read_options.read_tier && biter.status().IsIncomplete()) { // couldn't get block from block_cache // Update Saver.state to Found because we are only looking for whether // we can guarantee the key is not there when "no_io" is set get_context->MarkKeyMayExist(); break; } if (!biter.status().ok()) { s = biter.status(); break; } // Call the *saver function on each entry/block until it returns false for (biter.Seek(key); biter.Valid(); biter.Next()) { ParsedInternalKey parsed_key; if (!ParseInternalKey(biter.key(), &parsed_key)) { s = Status::Corruption(Slice()); } if (!get_context->SaveValue(parsed_key, biter.value())) { done = true; break; } } s = biter.status(); } } if (s.ok()) { s = iiter.status(); } } filter_entry.Release(rep_->table_options.block_cache.get()); return s; } bool BlockBasedTable::TEST_KeyInCache(const ReadOptions& options, const Slice& key) { std::unique_ptr iiter(NewIndexIterator(options)); iiter->Seek(key); assert(iiter->Valid()); CachableEntry block; BlockHandle handle; Slice input = iiter->value(); Status s = handle.DecodeFrom(&input); assert(s.ok()); Cache* block_cache = rep_->table_options.block_cache.get(); assert(block_cache != nullptr); char cache_key_storage[kMaxCacheKeyPrefixSize + kMaxVarint64Length]; Slice cache_key = GetCacheKey(rep_->cache_key_prefix, rep_->cache_key_prefix_size, handle, cache_key_storage); Slice ckey; s = GetDataBlockFromCache(cache_key, ckey, block_cache, nullptr, nullptr, options, &block, rep_->table_options.format_version); assert(s.ok()); bool in_cache = block.value != nullptr; if (in_cache) { ReleaseCachedEntry(block_cache, block.cache_handle); } return in_cache; } // REQUIRES: The following fields of rep_ should have already been populated: // 1. file // 2. index_handle, // 3. options // 4. internal_comparator // 5. index_type Status BlockBasedTable::CreateIndexReader(IndexReader** index_reader, Iterator* preloaded_meta_index_iter) { // Some old version of block-based tables don't have index type present in // table properties. If that's the case we can safely use the kBinarySearch. auto index_type_on_file = BlockBasedTableOptions::kBinarySearch; if (rep_->table_properties) { auto& props = rep_->table_properties->user_collected_properties; auto pos = props.find(BlockBasedTablePropertyNames::kIndexType); if (pos != props.end()) { index_type_on_file = static_cast( DecodeFixed32(pos->second.c_str())); } } auto file = rep_->file.get(); auto env = rep_->ioptions.env; auto comparator = &rep_->internal_comparator; const Footer& footer = rep_->footer; if (index_type_on_file == BlockBasedTableOptions::kHashSearch && rep_->ioptions.prefix_extractor == nullptr) { Log(InfoLogLevel::WARN_LEVEL, rep_->ioptions.info_log, "BlockBasedTableOptions::kHashSearch requires " "options.prefix_extractor to be set." " Fall back to binary seach index."); index_type_on_file = BlockBasedTableOptions::kBinarySearch; } switch (index_type_on_file) { case BlockBasedTableOptions::kBinarySearch: { return BinarySearchIndexReader::Create( file, footer, footer.index_handle(), env, comparator, index_reader); } case BlockBasedTableOptions::kHashSearch: { std::unique_ptr meta_guard; std::unique_ptr meta_iter_guard; auto meta_index_iter = preloaded_meta_index_iter; if (meta_index_iter == nullptr) { auto s = ReadMetaBlock(rep_, &meta_guard, &meta_iter_guard); if (!s.ok()) { // we simply fall back to binary search in case there is any // problem with prefix hash index loading. Log(InfoLogLevel::WARN_LEVEL, rep_->ioptions.info_log, "Unable to read the metaindex block." " Fall back to binary seach index."); return BinarySearchIndexReader::Create( file, footer, footer.index_handle(), env, comparator, index_reader); } meta_index_iter = meta_iter_guard.get(); } // We need to wrap data with internal_prefix_transform to make sure it can // handle prefix correctly. rep_->internal_prefix_transform.reset( new InternalKeySliceTransform(rep_->ioptions.prefix_extractor)); return HashIndexReader::Create( rep_->internal_prefix_transform.get(), footer, file, env, comparator, footer.index_handle(), meta_index_iter, index_reader, rep_->hash_index_allow_collision); } default: { std::string error_message = "Unrecognized index type: " + ToString(rep_->index_type); return Status::InvalidArgument(error_message.c_str()); } } } uint64_t BlockBasedTable::ApproximateOffsetOf(const Slice& key) { unique_ptr index_iter(NewIndexIterator(ReadOptions())); index_iter->Seek(key); uint64_t result; if (index_iter->Valid()) { BlockHandle handle; Slice input = index_iter->value(); Status s = handle.DecodeFrom(&input); if (s.ok()) { result = handle.offset(); } else { // Strange: we can't decode the block handle in the index block. // We'll just return the offset of the metaindex block, which is // close to the whole file size for this case. result = rep_->footer.metaindex_handle().offset(); } } else { // key is past the last key in the file. If table_properties is not // available, approximate the offset by returning the offset of the // metaindex block (which is right near the end of the file). result = 0; if (rep_->table_properties) { result = rep_->table_properties->data_size; } // table_properties is not present in the table. if (result == 0) { result = rep_->footer.metaindex_handle().offset(); } } return result; } bool BlockBasedTable::TEST_filter_block_preloaded() const { return rep_->filter != nullptr; } bool BlockBasedTable::TEST_index_reader_preloaded() const { return rep_->index_reader != nullptr; } Status BlockBasedTable::DumpTable(WritableFile* out_file) { // Output Footer out_file->Append( "Footer Details:\n" "--------------------------------------\n" " "); out_file->Append(rep_->footer.ToString().c_str()); out_file->Append("\n"); // Output MetaIndex out_file->Append( "Metaindex Details:\n" "--------------------------------------\n"); std::unique_ptr meta; std::unique_ptr meta_iter; Status s = ReadMetaBlock(rep_, &meta, &meta_iter); if (s.ok()) { for (meta_iter->SeekToFirst(); meta_iter->Valid(); meta_iter->Next()) { s = meta_iter->status(); if (!s.ok()) { return s; } if (meta_iter->key() == rocksdb::kPropertiesBlock) { out_file->Append(" Properties block handle: "); out_file->Append(meta_iter->value().ToString(true).c_str()); out_file->Append("\n"); } else if (strstr(meta_iter->key().ToString().c_str(), "filter.rocksdb.") != nullptr) { out_file->Append(" Filter block handle: "); out_file->Append(meta_iter->value().ToString(true).c_str()); out_file->Append("\n"); } } out_file->Append("\n"); } else { return s; } // Output TableProperties const rocksdb::TableProperties* table_properties; table_properties = rep_->table_properties.get(); if (table_properties != nullptr) { out_file->Append( "Table Properties:\n" "--------------------------------------\n" " "); out_file->Append(table_properties->ToString("\n ", ": ").c_str()); out_file->Append("\n"); } // Output Filter blocks if (!rep_->filter && !table_properties->filter_policy_name.empty()) { // Support only BloomFilter as off now rocksdb::BlockBasedTableOptions table_options; table_options.filter_policy.reset(rocksdb::NewBloomFilterPolicy(1)); if (table_properties->filter_policy_name.compare( table_options.filter_policy->Name()) == 0) { std::string filter_block_key = kFilterBlockPrefix; filter_block_key.append(table_properties->filter_policy_name); BlockHandle handle; if (FindMetaBlock(meta_iter.get(), filter_block_key, &handle).ok()) { BlockContents block; if (ReadBlockContents(rep_->file.get(), rep_->footer, ReadOptions(), handle, &block, rep_->ioptions.env, false).ok()) { rep_->filter.reset( new BlockBasedFilterBlockReader(rep_->ioptions.prefix_extractor, table_options, std::move(block))); } } } } if (rep_->filter) { out_file->Append( "Filter Details:\n" "--------------------------------------\n" " "); out_file->Append(rep_->filter->ToString().c_str()); out_file->Append("\n"); } // Output Index block s = DumpIndexBlock(out_file); if (!s.ok()) { return s; } // Output Data blocks s = DumpDataBlocks(out_file); return s; } Status BlockBasedTable::DumpIndexBlock(WritableFile* out_file) { out_file->Append( "Index Details:\n" "--------------------------------------\n"); std::unique_ptr blockhandles_iter(NewIndexIterator(ReadOptions())); Status s = blockhandles_iter->status(); if (!s.ok()) { out_file->Append("Can not read Index Block \n\n"); return s; } out_file->Append(" Block key hex dump: Data block handle\n"); out_file->Append(" Block key ascii\n\n"); for (blockhandles_iter->SeekToFirst(); blockhandles_iter->Valid(); blockhandles_iter->Next()) { s = blockhandles_iter->status(); if (!s.ok()) { break; } Slice key = blockhandles_iter->key(); InternalKey ikey; ikey.DecodeFrom(key); out_file->Append(" HEX "); out_file->Append(ikey.user_key().ToString(true).c_str()); out_file->Append(": "); out_file->Append(blockhandles_iter->value().ToString(true).c_str()); out_file->Append("\n"); std::string str_key = ikey.user_key().ToString(); std::string res_key(""); char cspace = ' '; for (size_t i = 0; i < str_key.size(); i++) { res_key.append(&str_key[i], 1); res_key.append(1, cspace); } out_file->Append(" ASCII "); out_file->Append(res_key.c_str()); out_file->Append("\n ------\n"); } out_file->Append("\n"); return Status::OK(); } Status BlockBasedTable::DumpDataBlocks(WritableFile* out_file) { std::unique_ptr blockhandles_iter(NewIndexIterator(ReadOptions())); Status s = blockhandles_iter->status(); if (!s.ok()) { out_file->Append("Can not read Index Block \n\n"); return s; } size_t block_id = 1; for (blockhandles_iter->SeekToFirst(); blockhandles_iter->Valid(); block_id++, blockhandles_iter->Next()) { s = blockhandles_iter->status(); if (!s.ok()) { break; } out_file->Append("Data Block # "); out_file->Append(std::to_string(block_id)); out_file->Append(" @ "); out_file->Append(blockhandles_iter->value().ToString(true).c_str()); out_file->Append("\n"); out_file->Append("--------------------------------------\n"); std::unique_ptr datablock_iter; datablock_iter.reset( NewDataBlockIterator(rep_, ReadOptions(), blockhandles_iter->value())); s = datablock_iter->status(); if (!s.ok()) { out_file->Append("Error reading the block - Skipped \n\n"); continue; } for (datablock_iter->SeekToFirst(); datablock_iter->Valid(); datablock_iter->Next()) { s = datablock_iter->status(); if (!s.ok()) { out_file->Append("Error reading the block - Skipped \n"); break; } Slice key = datablock_iter->key(); Slice value = datablock_iter->value(); InternalKey ikey, iValue; ikey.DecodeFrom(key); iValue.DecodeFrom(value); out_file->Append(" HEX "); out_file->Append(ikey.user_key().ToString(true).c_str()); out_file->Append(": "); out_file->Append(iValue.user_key().ToString(true).c_str()); out_file->Append("\n"); std::string str_key = ikey.user_key().ToString(); std::string str_value = iValue.user_key().ToString(); std::string res_key(""), res_value(""); char cspace = ' '; for (size_t i = 0; i < str_key.size(); i++) { res_key.append(&str_key[i], 1); res_key.append(1, cspace); } for (size_t i = 0; i < str_value.size(); i++) { res_value.append(&str_value[i], 1); res_value.append(1, cspace); } out_file->Append(" ASCII "); out_file->Append(res_key.c_str()); out_file->Append(": "); out_file->Append(res_value.c_str()); out_file->Append("\n ------\n"); } out_file->Append("\n"); } return Status::OK(); } } // namespace rocksdb