// 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 {
class Cache;
class FilterBlockReader;
class BlockBasedFilterBlockReader;
class FullFilterBlockReader;
class Footer;
class InternalKeyComparator;
class Iterator;
class RandomAccessFile;
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 ReadMetaBlock(FilePrefetchBuffer* prefetch_buffer,
std::unique_ptr<Block>* meta_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, RandomAccessFile* file,
char* buffer, size_t* size);
static void GenerateCachePrefix(Cache* cc, WritableFile* 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);
friend class PartitionedFilterBlockReader;
friend class PartitionedFilterBlockTest;
};
// 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.
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::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;
}
};
// 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 {
if (!index_iter_->status().ok()) {
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_;
}
bool CheckPrefixMayMatch(const Slice& ikey) {
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;
}
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:
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();
};
} // namespace rocksdb