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rocksdb/table/block.cc
Siying Dong 4479dff208 Reduce binary search when reseek into the same data block (#5256) 
Summary:
Right now, when Seek() is called again, RocksDB always does a binary search against the files and index blocks, even if they end up with the same file/block. Improve it as following:
1. in LevelIterator, reseek first try to check the boundary of the current file. If it falls into the same file, skip the binary search to find the file
2. in block based table iterator, reseek skip to reseek the iterator block if the seek key is larger than the current key and lower than the index key (boundary of the current block and the next block).
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5256

Differential Revision: D15105072

Pulled By: siying

fbshipit-source-id: 39634bdb4a881082451fa39cecd7ecf12160bf80
2019-05-01 14:26:30 -07:00

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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.
//
// Decodes the blocks generated by block_builder.cc.
#include "table/block.h"
#include <algorithm>
#include <string>
#include <unordered_map>
#include <vector>
#include "monitoring/perf_context_imp.h"
#include "port/port.h"
#include "port/stack_trace.h"
#include "rocksdb/comparator.h"
#include "table/block_prefix_index.h"
#include "table/data_block_footer.h"
#include "table/format.h"
#include "util/coding.h"
#include "util/logging.h"
namespace rocksdb {
// Helper routine: decode the next block entry starting at "p",
// storing the number of shared key bytes, non_shared key bytes,
// and the length of the value in "*shared", "*non_shared", and
// "*value_length", respectively. Will not derefence past "limit".
//
// If any errors are detected, returns nullptr. Otherwise, returns a
// pointer to the key delta (just past the three decoded values).
struct DecodeEntry {
inline const char* operator()(const char* p, const char* limit,
uint32_t* shared, uint32_t* non_shared,
uint32_t* value_length) {
// We need 2 bytes for shared and non_shared size. We also need one more
// byte either for value size or the actual value in case of value delta
// encoding.
assert(limit - p >= 3);
*shared = reinterpret_cast<const unsigned char*>(p)[0];
*non_shared = reinterpret_cast<const unsigned char*>(p)[1];
*value_length = reinterpret_cast<const unsigned char*>(p)[2];
if ((*shared | *non_shared | *value_length) < 128) {
// Fast path: all three values are encoded in one byte each
p += 3;
} else {
if ((p = GetVarint32Ptr(p, limit, shared)) == nullptr) return nullptr;
if ((p = GetVarint32Ptr(p, limit, non_shared)) == nullptr) return nullptr;
if ((p = GetVarint32Ptr(p, limit, value_length)) == nullptr) {
return nullptr;
}
}
// Using an assert in place of "return null" since we should not pay the
// cost of checking for corruption on every single key decoding
assert(!(static_cast<uint32_t>(limit - p) < (*non_shared + *value_length)));
return p;
}
};
// Helper routine: similar to DecodeEntry but does not have assertions.
// Instead, returns nullptr so that caller can detect and report failure.
struct CheckAndDecodeEntry {
inline const char* operator()(const char* p, const char* limit,
uint32_t* shared, uint32_t* non_shared,
uint32_t* value_length) {
// We need 2 bytes for shared and non_shared size. We also need one more
// byte either for value size or the actual value in case of value delta
// encoding.
if (limit - p < 3) {
return nullptr;
}
*shared = reinterpret_cast<const unsigned char*>(p)[0];
*non_shared = reinterpret_cast<const unsigned char*>(p)[1];
*value_length = reinterpret_cast<const unsigned char*>(p)[2];
if ((*shared | *non_shared | *value_length) < 128) {
// Fast path: all three values are encoded in one byte each
p += 3;
} else {
if ((p = GetVarint32Ptr(p, limit, shared)) == nullptr) return nullptr;
if ((p = GetVarint32Ptr(p, limit, non_shared)) == nullptr) return nullptr;
if ((p = GetVarint32Ptr(p, limit, value_length)) == nullptr) {
return nullptr;
}
}
if (static_cast<uint32_t>(limit - p) < (*non_shared + *value_length)) {
return nullptr;
}
return p;
}
};
struct DecodeKey {
inline const char* operator()(const char* p, const char* limit,
uint32_t* shared, uint32_t* non_shared) {
uint32_t value_length;
return DecodeEntry()(p, limit, shared, non_shared, &value_length);
}
};
// In format_version 4, which is used by index blocks, the value size is not
// encoded before the entry, as the value is known to be the handle with the
// known size.
struct DecodeKeyV4 {
inline const char* operator()(const char* p, const char* limit,
uint32_t* shared, uint32_t* non_shared) {
// We need 2 bytes for shared and non_shared size. We also need one more
// byte either for value size or the actual value in case of value delta
// encoding.
if (limit - p < 3) return nullptr;
*shared = reinterpret_cast<const unsigned char*>(p)[0];
*non_shared = reinterpret_cast<const unsigned char*>(p)[1];
if ((*shared | *non_shared) < 128) {
// Fast path: all three values are encoded in one byte each
p += 2;
} else {
if ((p = GetVarint32Ptr(p, limit, shared)) == nullptr) return nullptr;
if ((p = GetVarint32Ptr(p, limit, non_shared)) == nullptr) return nullptr;
}
return p;
}
};
void DataBlockIter::Next() {
assert(Valid());
ParseNextDataKey<DecodeEntry>();
}
void DataBlockIter::NextOrReport() {
assert(Valid());
ParseNextDataKey<CheckAndDecodeEntry>();
}
void IndexBlockIter::Next() {
assert(Valid());
ParseNextIndexKey();
}
void IndexBlockIter::Prev() {
assert(Valid());
// Scan backwards to a restart point before current_
const uint32_t original = current_;
while (GetRestartPoint(restart_index_) >= original) {
if (restart_index_ == 0) {
// No more entries
current_ = restarts_;
restart_index_ = num_restarts_;
return;
}
restart_index_--;
}
SeekToRestartPoint(restart_index_);
do {
if (!ParseNextIndexKey()) {
break;
}
// Loop until end of current entry hits the start of original entry
} while (NextEntryOffset() < original);
}
// Similar to IndexBlockIter::Prev but also caches the prev entries
void DataBlockIter::Prev() {
assert(Valid());
assert(prev_entries_idx_ == -1 ||
static_cast<size_t>(prev_entries_idx_) < prev_entries_.size());
// Check if we can use cached prev_entries_
if (prev_entries_idx_ > 0 &&
prev_entries_[prev_entries_idx_].offset == current_) {
// Read cached CachedPrevEntry
prev_entries_idx_--;
const CachedPrevEntry& current_prev_entry =
prev_entries_[prev_entries_idx_];
const char* key_ptr = nullptr;
if (current_prev_entry.key_ptr != nullptr) {
// The key is not delta encoded and stored in the data block
key_ptr = current_prev_entry.key_ptr;
key_pinned_ = true;
} else {
// The key is delta encoded and stored in prev_entries_keys_buff_
key_ptr = prev_entries_keys_buff_.data() + current_prev_entry.key_offset;
key_pinned_ = false;
}
const Slice current_key(key_ptr, current_prev_entry.key_size);
current_ = current_prev_entry.offset;
key_.SetKey(current_key, false /* copy */);
value_ = current_prev_entry.value;
return;
}
// Clear prev entries cache
prev_entries_idx_ = -1;
prev_entries_.clear();
prev_entries_keys_buff_.clear();
// Scan backwards to a restart point before current_
const uint32_t original = current_;
while (GetRestartPoint(restart_index_) >= original) {
if (restart_index_ == 0) {
// No more entries
current_ = restarts_;
restart_index_ = num_restarts_;
return;
}
restart_index_--;
}
SeekToRestartPoint(restart_index_);
do {
if (!ParseNextDataKey<DecodeEntry>()) {
break;
}
Slice current_key = key();
if (key_.IsKeyPinned()) {
// The key is not delta encoded
prev_entries_.emplace_back(current_, current_key.data(), 0,
current_key.size(), value());
} else {
// The key is delta encoded, cache decoded key in buffer
size_t new_key_offset = prev_entries_keys_buff_.size();
prev_entries_keys_buff_.append(current_key.data(), current_key.size());
prev_entries_.emplace_back(current_, nullptr, new_key_offset,
current_key.size(), value());
}
// Loop until end of current entry hits the start of original entry
} while (NextEntryOffset() < original);
prev_entries_idx_ = static_cast<int32_t>(prev_entries_.size()) - 1;
}
void DataBlockIter::Seek(const Slice& target) {
Slice seek_key = target;
PERF_TIMER_GUARD(block_seek_nanos);
if (data_ == nullptr) { // Not init yet
return;
}
uint32_t index = 0;
bool ok = BinarySeek<DecodeKey>(seek_key, 0, num_restarts_ - 1, &index,
comparator_);
if (!ok) {
return;
}
SeekToRestartPoint(index);
// Linear search (within restart block) for first key >= target
while (true) {
if (!ParseNextDataKey<DecodeEntry>() || Compare(key_, seek_key) >= 0) {
return;
}
}
}
// Optimized Seek for point lookup for an internal key `target`
// target = "seek_user_key @ type | seqno".
//
// For any type other than kTypeValue, kTypeDeletion, kTypeSingleDeletion,
// or kTypeBlobIndex, this function behaves identically as Seek().
//
// For any type in kTypeValue, kTypeDeletion, kTypeSingleDeletion,
// or kTypeBlobIndex:
//
// If the return value is FALSE, iter location is undefined, and it means:
// 1) there is no key in this block falling into the range:
// ["seek_user_key @ type | seqno", "seek_user_key @ kTypeDeletion | 0"],
// inclusive; AND
// 2) the last key of this block has a greater user_key from seek_user_key
//
// If the return value is TRUE, iter location has two possibilies:
// 1) If iter is valid, it is set to a location as if set by BinarySeek. In
// this case, it points to the first key_ with a larger user_key or a
// matching user_key with a seqno no greater than the seeking seqno.
// 2) If the iter is invalid, it means that either all the user_key is less
// than the seek_user_key, or the block ends with a matching user_key but
// with a smaller [ type | seqno ] (i.e. a larger seqno, or the same seqno
// but larger type).
bool DataBlockIter::SeekForGetImpl(const Slice& target) {
Slice target_user_key = ExtractUserKey(target);
uint32_t map_offset = restarts_ + num_restarts_ * sizeof(uint32_t);
uint8_t entry =
data_block_hash_index_->Lookup(data_, map_offset, target_user_key);
if (entry == kCollision) {
// HashSeek not effective, falling back
Seek(target);
return true;
}
if (entry == kNoEntry) {
// Even if we cannot find the user_key in this block, the result may
// exist in the next block. Consider this exmpale:
//
// Block N: [aab@100, ... , app@120]
// bounary key: axy@50 (we make minimal assumption about a boundary key)
// Block N+1: [axy@10, ... ]
//
// If seek_key = axy@60, the search will starts from Block N.
// Even if the user_key is not found in the hash map, the caller still
// have to conntinue searching the next block.
//
// In this case, we pretend the key is the the last restart interval.
// The while-loop below will search the last restart interval for the
// key. It will stop at the first key that is larger than the seek_key,
// or to the end of the block if no one is larger.
entry = static_cast<uint8_t>(num_restarts_ - 1);
}
uint32_t restart_index = entry;
// check if the key is in the restart_interval
assert(restart_index < num_restarts_);
SeekToRestartPoint(restart_index);
const char* limit = nullptr;
if (restart_index_ + 1 < num_restarts_) {
limit = data_ + GetRestartPoint(restart_index_ + 1);
} else {
limit = data_ + restarts_;
}
while (true) {
// Here we only linear seek the target key inside the restart interval.
// If a key does not exist inside a restart interval, we avoid
// further searching the block content accross restart interval boundary.
//
// TODO(fwu): check the left and write boundary of the restart interval
// to avoid linear seek a target key that is out of range.
if (!ParseNextDataKey<DecodeEntry>(limit) || Compare(key_, target) >= 0) {
// we stop at the first potential matching user key.
break;
}
}
if (current_ == restarts_) {
// Search reaches to the end of the block. There are three possibilites:
// 1) there is only one user_key match in the block (otherwise collsion).
// the matching user_key resides in the last restart interval, and it
// is the last key of the restart interval and of the block as well.
// ParseNextDataKey() skiped it as its [ type | seqno ] is smaller.
//
// 2) The seek_key is not found in the HashIndex Lookup(), i.e. kNoEntry,
// AND all existing user_keys in the restart interval are smaller than
// seek_user_key.
//
// 3) The seek_key is a false positive and happens to be hashed to the
// last restart interval, AND all existing user_keys in the restart
// interval are smaller than seek_user_key.
//
// The result may exist in the next block each case, so we return true.
return true;
}
if (user_comparator_->Compare(key_.GetUserKey(), target_user_key) != 0) {
// the key is not in this block and cannot be at the next block either.
return false;
}
// Here we are conservative and only support a limited set of cases
ValueType value_type = ExtractValueType(key_.GetKey());
if (value_type != ValueType::kTypeValue &&
value_type != ValueType::kTypeDeletion &&
value_type != ValueType::kTypeSingleDeletion &&
value_type != ValueType::kTypeBlobIndex) {
Seek(target);
return true;
}
// Result found, and the iter is correctly set.
return true;
}
void IndexBlockIter::Seek(const Slice& target) {
TEST_SYNC_POINT("IndexBlockIter::Seek:0");
Slice seek_key = target;
if (!key_includes_seq_) {
seek_key = ExtractUserKey(target);
}
PERF_TIMER_GUARD(block_seek_nanos);
if (data_ == nullptr) { // Not init yet
return;
}
uint32_t index = 0;
bool ok = false;
if (prefix_index_) {
ok = PrefixSeek(target, &index);
} else if (value_delta_encoded_) {
ok = BinarySeek<DecodeKeyV4>(seek_key, 0, num_restarts_ - 1, &index,
comparator_);
} else {
ok = BinarySeek<DecodeKey>(seek_key, 0, num_restarts_ - 1, &index,
comparator_);
}
if (!ok) {
return;
}
SeekToRestartPoint(index);
// Linear search (within restart block) for first key >= target
while (true) {
if (!ParseNextIndexKey() || Compare(key_, seek_key) >= 0) {
return;
}
}
}
void DataBlockIter::SeekForPrev(const Slice& target) {
PERF_TIMER_GUARD(block_seek_nanos);
Slice seek_key = target;
if (data_ == nullptr) { // Not init yet
return;
}
uint32_t index = 0;
bool ok = BinarySeek<DecodeKey>(seek_key, 0, num_restarts_ - 1, &index,
comparator_);
if (!ok) {
return;
}
SeekToRestartPoint(index);
// Linear search (within restart block) for first key >= seek_key
while (ParseNextDataKey<DecodeEntry>() && Compare(key_, seek_key) < 0) {
}
if (!Valid()) {
SeekToLast();
} else {
while (Valid() && Compare(key_, seek_key) > 0) {
Prev();
}
}
}
void DataBlockIter::SeekToFirst() {
if (data_ == nullptr) { // Not init yet
return;
}
SeekToRestartPoint(0);
ParseNextDataKey<DecodeEntry>();
}
void DataBlockIter::SeekToFirstOrReport() {
if (data_ == nullptr) { // Not init yet
return;
}
SeekToRestartPoint(0);
ParseNextDataKey<CheckAndDecodeEntry>();
}
void IndexBlockIter::SeekToFirst() {
if (data_ == nullptr) { // Not init yet
return;
}
SeekToRestartPoint(0);
ParseNextIndexKey();
}
void DataBlockIter::SeekToLast() {
if (data_ == nullptr) { // Not init yet
return;
}
SeekToRestartPoint(num_restarts_ - 1);
while (ParseNextDataKey<DecodeEntry>() && NextEntryOffset() < restarts_) {
// Keep skipping
}
}
void IndexBlockIter::SeekToLast() {
if (data_ == nullptr) { // Not init yet
return;
}
SeekToRestartPoint(num_restarts_ - 1);
while (ParseNextIndexKey() && NextEntryOffset() < restarts_) {
// Keep skipping
}
}
template <class TValue>
void BlockIter<TValue>::CorruptionError() {
current_ = restarts_;
restart_index_ = num_restarts_;
status_ = Status::Corruption("bad entry in block");
key_.Clear();
value_.clear();
}
template <typename DecodeEntryFunc>
bool DataBlockIter::ParseNextDataKey(const char* limit) {
current_ = NextEntryOffset();
const char* p = data_ + current_;
if (!limit) {
limit = data_ + restarts_; // Restarts come right after data
}
if (p >= limit) {
// No more entries to return. Mark as invalid.
current_ = restarts_;
restart_index_ = num_restarts_;
return false;
}
// Decode next entry
uint32_t shared, non_shared, value_length;
p = DecodeEntryFunc()(p, limit, &shared, &non_shared, &value_length);
if (p == nullptr || key_.Size() < shared) {
CorruptionError();
return false;
} else {
if (shared == 0) {
// If this key dont share any bytes with prev key then we dont need
// to decode it and can use it's address in the block directly.
key_.SetKey(Slice(p, non_shared), false /* copy */);
key_pinned_ = true;
} else {
// This key share `shared` bytes with prev key, we need to decode it
key_.TrimAppend(shared, p, non_shared);
key_pinned_ = false;
}
if (global_seqno_ != kDisableGlobalSequenceNumber) {
// If we are reading a file with a global sequence number we should
// expect that all encoded sequence numbers are zeros and any value
// type is kTypeValue, kTypeMerge, kTypeDeletion, or kTypeRangeDeletion.
assert(GetInternalKeySeqno(key_.GetInternalKey()) == 0);
ValueType value_type = ExtractValueType(key_.GetKey());
assert(value_type == ValueType::kTypeValue ||
value_type == ValueType::kTypeMerge ||
value_type == ValueType::kTypeDeletion ||
value_type == ValueType::kTypeRangeDeletion);
if (key_pinned_) {
// TODO(tec): Investigate updating the seqno in the loaded block
// directly instead of doing a copy and update.
// We cannot use the key address in the block directly because
// we have a global_seqno_ that will overwrite the encoded one.
key_.OwnKey();
key_pinned_ = false;
}
key_.UpdateInternalKey(global_seqno_, value_type);
}
value_ = Slice(p + non_shared, value_length);
if (shared == 0) {
while (restart_index_ + 1 < num_restarts_ &&
GetRestartPoint(restart_index_ + 1) < current_) {
++restart_index_;
}
}
// else we are in the middle of a restart interval and the restart_index_
// thus has not changed
return true;
}
}
bool IndexBlockIter::ParseNextIndexKey() {
current_ = NextEntryOffset();
const char* p = data_ + current_;
const char* limit = data_ + restarts_; // Restarts come right after data
if (p >= limit) {
// No more entries to return. Mark as invalid.
current_ = restarts_;
restart_index_ = num_restarts_;
return false;
}
// Decode next entry
uint32_t shared, non_shared, value_length;
if (value_delta_encoded_) {
p = DecodeKeyV4()(p, limit, &shared, &non_shared);
value_length = 0;
} else {
p = DecodeEntry()(p, limit, &shared, &non_shared, &value_length);
}
if (p == nullptr || key_.Size() < shared) {
CorruptionError();
return false;
}
if (shared == 0) {
// If this key dont share any bytes with prev key then we dont need
// to decode it and can use it's address in the block directly.
key_.SetKey(Slice(p, non_shared), false /* copy */);
key_pinned_ = true;
} else {
// This key share `shared` bytes with prev key, we need to decode it
key_.TrimAppend(shared, p, non_shared);
key_pinned_ = false;
}
value_ = Slice(p + non_shared, value_length);
if (shared == 0) {
while (restart_index_ + 1 < num_restarts_ &&
GetRestartPoint(restart_index_ + 1) < current_) {
++restart_index_;
}
}
// else we are in the middle of a restart interval and the restart_index_
// thus has not changed
if (value_delta_encoded_) {
assert(value_length == 0);
DecodeCurrentValue(shared);
}
return true;
}
// The format:
// restart_point 0: k, v (off, sz), k, v (delta-sz), ..., k, v (delta-sz)
// restart_point 1: k, v (off, sz), k, v (delta-sz), ..., k, v (delta-sz)
// ...
// restart_point n-1: k, v (off, sz), k, v (delta-sz), ..., k, v (delta-sz)
// where, k is key, v is value, and its encoding is in parenthesis.
// The format of each key is (shared_size, non_shared_size, shared, non_shared)
// The format of each value, i.e., block hanlde, is (offset, size) whenever the
// shared_size is 0, which included the first entry in each restart point.
// Otherwise the format is delta-size = block handle size - size of last block
// handle.
void IndexBlockIter::DecodeCurrentValue(uint32_t shared) {
assert(value_delta_encoded_);
const char* limit = data_ + restarts_;
if (shared == 0) {
uint64_t o, s;
const char* newp = GetVarint64Ptr(value_.data(), limit, &o);
assert(newp);
newp = GetVarint64Ptr(newp, limit, &s);
assert(newp);
decoded_value_ = BlockHandle(o, s);
value_ = Slice(value_.data(), newp - value_.data());
} else {
uint64_t next_value_base =
decoded_value_.offset() + decoded_value_.size() + kBlockTrailerSize;
int64_t delta;
const char* newp = GetVarsignedint64Ptr(value_.data(), limit, &delta);
decoded_value_ =
BlockHandle(next_value_base, decoded_value_.size() + delta);
value_ = Slice(value_.data(), newp - value_.data());
}
}
// Binary search in restart array to find the first restart point that
// is either the last restart point with a key less than target,
// which means the key of next restart point is larger than target, or
// the first restart point with a key = target
template <class TValue>
template <typename DecodeKeyFunc>
bool BlockIter<TValue>::BinarySeek(const Slice& target, uint32_t left,
uint32_t right, uint32_t* index,
const Comparator* comp) {
assert(left <= right);
while (left < right) {
uint32_t mid = (left + right + 1) / 2;
uint32_t region_offset = GetRestartPoint(mid);
uint32_t shared, non_shared;
const char* key_ptr = DecodeKeyFunc()(
data_ + region_offset, data_ + restarts_, &shared, &non_shared);
if (key_ptr == nullptr || (shared != 0)) {
CorruptionError();
return false;
}
Slice mid_key(key_ptr, non_shared);
int cmp = comp->Compare(mid_key, target);
if (cmp < 0) {
// Key at "mid" is smaller than "target". Therefore all
// blocks before "mid" are uninteresting.
left = mid;
} else if (cmp > 0) {
// Key at "mid" is >= "target". Therefore all blocks at or
// after "mid" are uninteresting.
right = mid - 1;
} else {
left = right = mid;
}
}
*index = left;
return true;
}
// Compare target key and the block key of the block of `block_index`.
// Return -1 if error.
int IndexBlockIter::CompareBlockKey(uint32_t block_index, const Slice& target) {
uint32_t region_offset = GetRestartPoint(block_index);
uint32_t shared, non_shared;
const char* key_ptr =
value_delta_encoded_
? DecodeKeyV4()(data_ + region_offset, data_ + restarts_, &shared,
&non_shared)
: DecodeKey()(data_ + region_offset, data_ + restarts_, &shared,
&non_shared);
if (key_ptr == nullptr || (shared != 0)) {
CorruptionError();
return 1; // Return target is smaller
}
Slice block_key(key_ptr, non_shared);
return Compare(block_key, target);
}
// Binary search in block_ids to find the first block
// with a key >= target
bool IndexBlockIter::BinaryBlockIndexSeek(const Slice& target,
uint32_t* block_ids, uint32_t left,
uint32_t right, uint32_t* index) {
assert(left <= right);
uint32_t left_bound = left;
while (left <= right) {
uint32_t mid = (right + left) / 2;
int cmp = CompareBlockKey(block_ids[mid], target);
if (!status_.ok()) {
return false;
}
if (cmp < 0) {
// Key at "target" is larger than "mid". Therefore all
// blocks before or at "mid" are uninteresting.
left = mid + 1;
} else {
// Key at "target" is <= "mid". Therefore all blocks
// after "mid" are uninteresting.
// If there is only one block left, we found it.
if (left == right) break;
right = mid;
}
}
if (left == right) {
// In one of the two following cases:
// (1) left is the first one of block_ids
// (2) there is a gap of blocks between block of `left` and `left-1`.
// we can further distinguish the case of key in the block or key not
// existing, by comparing the target key and the key of the previous
// block to the left of the block found.
if (block_ids[left] > 0 &&
(left == left_bound || block_ids[left - 1] != block_ids[left] - 1) &&
CompareBlockKey(block_ids[left] - 1, target) > 0) {
current_ = restarts_;
return false;
}
*index = block_ids[left];
return true;
} else {
assert(left > right);
// Mark iterator invalid
current_ = restarts_;
return false;
}
}
bool IndexBlockIter::PrefixSeek(const Slice& target, uint32_t* index) {
assert(prefix_index_);
Slice seek_key = target;
if (!key_includes_seq_) {
seek_key = ExtractUserKey(target);
}
uint32_t* block_ids = nullptr;
uint32_t num_blocks = prefix_index_->GetBlocks(target, &block_ids);
if (num_blocks == 0) {
current_ = restarts_;
return false;
} else {
return BinaryBlockIndexSeek(seek_key, block_ids, 0, num_blocks - 1, index);
}
}
uint32_t Block::NumRestarts() const {
assert(size_ >= 2 * sizeof(uint32_t));
uint32_t block_footer = DecodeFixed32(data_ + size_ - sizeof(uint32_t));
uint32_t num_restarts = block_footer;
if (size_ > kMaxBlockSizeSupportedByHashIndex) {
// In BlockBuilder, we have ensured a block with HashIndex is less than
// kMaxBlockSizeSupportedByHashIndex (64KiB).
//
// Therefore, if we encounter a block with a size > 64KiB, the block
// cannot have HashIndex. So the footer will directly interpreted as
// num_restarts.
//
// Such check is for backward compatibility. We can ensure legacy block
// with a vary large num_restarts i.e. >= 0x80000000 can be interpreted
// correctly as no HashIndex even if the MSB of num_restarts is set.
return num_restarts;
}
BlockBasedTableOptions::DataBlockIndexType index_type;
UnPackIndexTypeAndNumRestarts(block_footer, &index_type, &num_restarts);
return num_restarts;
}
BlockBasedTableOptions::DataBlockIndexType Block::IndexType() const {
assert(size_ >= 2 * sizeof(uint32_t));
if (size_ > kMaxBlockSizeSupportedByHashIndex) {
// The check is for the same reason as that in NumRestarts()
return BlockBasedTableOptions::kDataBlockBinarySearch;
}
uint32_t block_footer = DecodeFixed32(data_ + size_ - sizeof(uint32_t));
uint32_t num_restarts = block_footer;
BlockBasedTableOptions::DataBlockIndexType index_type;
UnPackIndexTypeAndNumRestarts(block_footer, &index_type, &num_restarts);
return index_type;
}
Block::~Block() {
// This sync point can be re-enabled if RocksDB can control the
// initialization order of any/all static options created by the user.
// TEST_SYNC_POINT("Block::~Block");
}
Block::Block(BlockContents&& contents, SequenceNumber _global_seqno,
size_t read_amp_bytes_per_bit, Statistics* statistics)
: contents_(std::move(contents)),
data_(contents_.data.data()),
size_(contents_.data.size()),
restart_offset_(0),
num_restarts_(0),
global_seqno_(_global_seqno) {
TEST_SYNC_POINT("Block::Block:0");
if (size_ < sizeof(uint32_t)) {
size_ = 0; // Error marker
} else {
// Should only decode restart points for uncompressed blocks
num_restarts_ = NumRestarts();
switch (IndexType()) {
case BlockBasedTableOptions::kDataBlockBinarySearch:
restart_offset_ = static_cast<uint32_t>(size_) -
(1 + num_restarts_) * sizeof(uint32_t);
if (restart_offset_ > size_ - sizeof(uint32_t)) {
// The size is too small for NumRestarts() and therefore
// restart_offset_ wrapped around.
size_ = 0;
}
break;
case BlockBasedTableOptions::kDataBlockBinaryAndHash:
if (size_ < sizeof(uint32_t) /* block footer */ +
sizeof(uint16_t) /* NUM_BUCK */) {
size_ = 0;
break;
}
uint16_t map_offset;
data_block_hash_index_.Initialize(
contents.data.data(),
static_cast<uint16_t>(contents.data.size() -
sizeof(uint32_t)), /*chop off
NUM_RESTARTS*/
&map_offset);
restart_offset_ = map_offset - num_restarts_ * sizeof(uint32_t);
if (restart_offset_ > map_offset) {
// map_offset is too small for NumRestarts() and
// therefore restart_offset_ wrapped around.
size_ = 0;
break;
}
break;
default:
size_ = 0; // Error marker
}
}
if (read_amp_bytes_per_bit != 0 && statistics && size_ != 0) {
read_amp_bitmap_.reset(new BlockReadAmpBitmap(
restart_offset_, read_amp_bytes_per_bit, statistics));
}
}
template <>
DataBlockIter* Block::NewIterator(const Comparator* cmp, const Comparator* ucmp,
DataBlockIter* iter, Statistics* stats,
bool /*total_order_seek*/,
bool /*key_includes_seq*/,
bool /*value_is_full*/,
bool block_contents_pinned,
BlockPrefixIndex* /*prefix_index*/) {
DataBlockIter* ret_iter;
if (iter != nullptr) {
ret_iter = iter;
} else {
ret_iter = new DataBlockIter;
}
if (size_ < 2 * sizeof(uint32_t)) {
ret_iter->Invalidate(Status::Corruption("bad block contents"));
return ret_iter;
}
if (num_restarts_ == 0) {
// Empty block.
ret_iter->Invalidate(Status::OK());
return ret_iter;
} else {
ret_iter->Initialize(
cmp, ucmp, data_, restart_offset_, num_restarts_, global_seqno_,
read_amp_bitmap_.get(), block_contents_pinned,
data_block_hash_index_.Valid() ? &data_block_hash_index_ : nullptr);
if (read_amp_bitmap_) {
if (read_amp_bitmap_->GetStatistics() != stats) {
// DB changed the Statistics pointer, we need to notify read_amp_bitmap_
read_amp_bitmap_->SetStatistics(stats);
}
}
}
return ret_iter;
}
template <>
IndexBlockIter* Block::NewIterator(const Comparator* cmp,
const Comparator* ucmp, IndexBlockIter* iter,
Statistics* /*stats*/, bool total_order_seek,
bool key_includes_seq, bool value_is_full,
bool block_contents_pinned,
BlockPrefixIndex* prefix_index) {
IndexBlockIter* ret_iter;
if (iter != nullptr) {
ret_iter = iter;
} else {
ret_iter = new IndexBlockIter;
}
if (size_ < 2 * sizeof(uint32_t)) {
ret_iter->Invalidate(Status::Corruption("bad block contents"));
return ret_iter;
}
if (num_restarts_ == 0) {
// Empty block.
ret_iter->Invalidate(Status::OK());
return ret_iter;
} else {
BlockPrefixIndex* prefix_index_ptr =
total_order_seek ? nullptr : prefix_index;
ret_iter->Initialize(cmp, ucmp, data_, restart_offset_, num_restarts_,
prefix_index_ptr, key_includes_seq, value_is_full,
block_contents_pinned,
nullptr /* data_block_hash_index */);
}
return ret_iter;
}
size_t Block::ApproximateMemoryUsage() const {
size_t usage = usable_size();
#ifdef ROCKSDB_MALLOC_USABLE_SIZE
usage += malloc_usable_size((void*)this);
#else
usage += sizeof(*this);
#endif // ROCKSDB_MALLOC_USABLE_SIZE
if (read_amp_bitmap_) {
usage += read_amp_bitmap_->ApproximateMemoryUsage();
}
return usage;
}
} // namespace rocksdb
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