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rocksdb/table/block_based/block_based_table_reader.h
Levi Tamasi 092f417037 Move the uncompression dictionary object out of the block cache (#5584) 
Summary:
RocksDB has historically stored uncompression dictionary objects in the block
cache as opposed to storing just the block contents. This neccesitated
evicting the object upon table close. With the new code, only the raw blocks
are stored in the cache, eliminating the need for eviction.

In addition, the patch makes the following improvements:

1) Compression dictionary blocks are now prefetched/pinned similarly to
index/filter blocks.
2) A copy operation got eliminated when the uncompression dictionary is
retrieved.
3) Errors related to retrieving the uncompression dictionary are propagated as
opposed to silently ignored.

Note: the patch temporarily breaks the compression dictionary evicition stats.
They will be fixed in a separate phase.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5584

Test Plan: make asan_check

Differential Revision: D16344151

Pulled By: ltamasi

fbshipit-source-id: 2962b295f5b19628f9da88a3fcebbce5a5017a7b
2019-07-23 16:01:44 -07:00

793 lines
33 KiB
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// 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 "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/file_reader_writer.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;
// 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;
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(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) {}
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 = false) const;
Status GetDataBlockFromCache(
const ReadOptions& ro, const BlockHandle& handle,
const UncompressionDict& uncompression_dict,
CachableEntry<Block>* block_entry, BlockType block_type,
GetContext* get_context) const;
void MaybeLoadBlocksToCache(
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(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);
// 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);
// No copying allowed
explicit BlockBasedTable(const TableReader&) = delete;
void operator=(const TableReader&) = delete;
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)
: InternalIteratorBase<TValue>(false),
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_;
// 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;
size_t readahead_size_ = 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
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