dolysis
/
rocksdb
mirror of https://github.com/facebook/rocksdb.git
3
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity
rocksdb/table/block.cc

726 lines
23 KiB
C++
Raw Blame History

// 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/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;
}
};
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();
}
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()) {
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() || Compare(key_, seek_key) >= 0) {
return;
}
}
}
void IndexBlockIter::Seek(const Slice& target) {
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,
active_comparator_);
} else {
ok = BinarySeek<DecodeKey>(seek_key, 0, num_restarts_ - 1, &index,
active_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() && 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();
}
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() && 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();
}
bool DataBlockIter::ParseNextDataKey() {
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;
p = DecodeEntry()(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));
return DecodeFixed32(data_ + size_ - sizeof(uint32_t));
}
Block::~Block() { 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
if (compression_type() == kNoCompression) {
num_restarts_ = NumRestarts();
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;
}
}
}
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*/,
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(), cachable());
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,
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,
cachable());
}
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
Reference in New Issue View Git Blame Copy Permalink