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rocksdb/table/cuckoo/cuckoo_table_builder.cc

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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).
#ifndef ROCKSDB_LITE
#include "table/cuckoo/cuckoo_table_builder.h"
#include <assert.h>
#include <algorithm>
#include <limits>
#include <string>
#include <vector>
#include "db/dbformat.h"
#include "file/writable_file_writer.h"
#include "rocksdb/env.h"
#include "rocksdb/table.h"
#include "table/block_based/block_builder.h"
#include "table/cuckoo/cuckoo_table_factory.h"
#include "table/format.h"
#include "table/meta_blocks.h"
#include "util/autovector.h"
#include "util/random.h"
#include "util/string_util.h"
namespace ROCKSDB_NAMESPACE {
const std::string CuckooTablePropertyNames::kEmptyKey =
"rocksdb.cuckoo.bucket.empty.key";
const std::string CuckooTablePropertyNames::kNumHashFunc =
"rocksdb.cuckoo.hash.num";
const std::string CuckooTablePropertyNames::kHashTableSize =
"rocksdb.cuckoo.hash.size";
const std::string CuckooTablePropertyNames::kValueLength =
"rocksdb.cuckoo.value.length";
const std::string CuckooTablePropertyNames::kIsLastLevel =
"rocksdb.cuckoo.file.islastlevel";
const std::string CuckooTablePropertyNames::kCuckooBlockSize =
"rocksdb.cuckoo.hash.cuckooblocksize";
const std::string CuckooTablePropertyNames::kIdentityAsFirstHash =
"rocksdb.cuckoo.hash.identityfirst";
const std::string CuckooTablePropertyNames::kUseModuleHash =
"rocksdb.cuckoo.hash.usemodule";
const std::string CuckooTablePropertyNames::kUserKeyLength =
"rocksdb.cuckoo.hash.userkeylength";
// Obtained by running echo rocksdb.table.cuckoo | sha1sum
extern const uint64_t kCuckooTableMagicNumber = 0x926789d0c5f17873ull;
CuckooTableBuilder::CuckooTableBuilder(
WritableFileWriter* file, double max_hash_table_ratio,
uint32_t max_num_hash_table, uint32_t max_search_depth,
const Comparator* user_comparator, uint32_t cuckoo_block_size,
bool use_module_hash, bool identity_as_first_hash,
uint64_t (*get_slice_hash)(const Slice&, uint32_t, uint64_t),
uint32_t column_family_id, const std::string& column_family_name,
const std::string& db_id, const std::string& db_session_id,
uint64_t file_number)
: num_hash_func_(2),
file_(file),
max_hash_table_ratio_(max_hash_table_ratio),
max_num_hash_func_(max_num_hash_table),
max_search_depth_(max_search_depth),
cuckoo_block_size_(std::max(1U, cuckoo_block_size)),
hash_table_size_(use_module_hash ? 0 : 2),
is_last_level_file_(false),
has_seen_first_key_(false),
has_seen_first_value_(false),
key_size_(0),
value_size_(0),
num_entries_(0),
num_values_(0),
ucomp_(user_comparator),
use_module_hash_(use_module_hash),
identity_as_first_hash_(identity_as_first_hash),
get_slice_hash_(get_slice_hash),
closed_(false) {
// Data is in a huge block.
properties_.num_data_blocks = 1;
properties_.index_size = 0;
properties_.filter_size = 0;
properties_.column_family_id = column_family_id;
properties_.column_family_name = column_family_name;
properties_.db_id = db_id;
properties_.db_session_id = db_session_id;
properties_.orig_file_number = file_number;
status_.PermitUncheckedError();
io_status_.PermitUncheckedError();
}
void CuckooTableBuilder::Add(const Slice& key, const Slice& value) {
if (num_entries_ >= kMaxVectorIdx - 1) {
status_ = Status::NotSupported("Number of keys in a file must be < 2^32-1");
return;
}
ParsedInternalKey ikey;
Status pik_status =
ParseInternalKey(key, &ikey, false /* log_err_key */); // TODO
if (!pik_status.ok()) {
status_ = Status::Corruption("Unable to parse key into internal key. ",
pik_status.getState());
return;
}
if (ikey.type != kTypeDeletion && ikey.type != kTypeValue) {
status_ = Status::NotSupported("Unsupported key type " +
std::to_string(ikey.type));
return;
}
// Determine if we can ignore the sequence number and value type from
// internal keys by looking at sequence number from first key. We assume
// that if first key has a zero sequence number, then all the remaining
// keys will have zero seq. no.
if (!has_seen_first_key_) {
is_last_level_file_ = ikey.sequence == 0;
has_seen_first_key_ = true;
smallest_user_key_.assign(ikey.user_key.data(), ikey.user_key.size());
largest_user_key_.assign(ikey.user_key.data(), ikey.user_key.size());
key_size_ = is_last_level_file_ ? ikey.user_key.size() : key.size();
}
if (key_size_ != (is_last_level_file_ ? ikey.user_key.size() : key.size())) {
status_ = Status::NotSupported("all keys have to be the same size");
return;
}
if (ikey.type == kTypeValue) {
if (!has_seen_first_value_) {
has_seen_first_value_ = true;
value_size_ = value.size();
}
if (value_size_ != value.size()) {
status_ = Status::NotSupported("all values have to be the same size");
return;
}
if (is_last_level_file_) {
kvs_.append(ikey.user_key.data(), ikey.user_key.size());
} else {
kvs_.append(key.data(), key.size());
}
kvs_.append(value.data(), value.size());
++num_values_;
} else {
if (is_last_level_file_) {
deleted_keys_.append(ikey.user_key.data(), ikey.user_key.size());
} else {
deleted_keys_.append(key.data(), key.size());
}
}
++num_entries_;
// In order to fill the empty buckets in the hash table, we identify a
// key which is not used so far (unused_user_key). We determine this by
// maintaining smallest and largest keys inserted so far in bytewise order
// and use them to find a key outside this range in Finish() operation.
// Note that this strategy is independent of user comparator used here.
if (ikey.user_key.compare(smallest_user_key_) < 0) {
smallest_user_key_.assign(ikey.user_key.data(), ikey.user_key.size());
} else if (ikey.user_key.compare(largest_user_key_) > 0) {
largest_user_key_.assign(ikey.user_key.data(), ikey.user_key.size());
}
if (!use_module_hash_) {
if (hash_table_size_ < num_entries_ / max_hash_table_ratio_) {
hash_table_size_ *= 2;
}
}
}
bool CuckooTableBuilder::IsDeletedKey(uint64_t idx) const {
assert(closed_);
return idx >= num_values_;
}
Slice CuckooTableBuilder::GetKey(uint64_t idx) const {
assert(closed_);
if (IsDeletedKey(idx)) {
return Slice(
&deleted_keys_[static_cast<size_t>((idx - num_values_) * key_size_)],
static_cast<size_t>(key_size_));
}
return Slice(&kvs_[static_cast<size_t>(idx * (key_size_ + value_size_))],
static_cast<size_t>(key_size_));
}
Slice CuckooTableBuilder::GetUserKey(uint64_t idx) const {
assert(closed_);
return is_last_level_file_ ? GetKey(idx) : ExtractUserKey(GetKey(idx));
}
Slice CuckooTableBuilder::GetValue(uint64_t idx) const {
assert(closed_);
if (IsDeletedKey(idx)) {
static std::string empty_value(static_cast<unsigned int>(value_size_), 'a');
return Slice(empty_value);
}
return Slice(
&kvs_[static_cast<size_t>(idx * (key_size_ + value_size_) + key_size_)],
static_cast<size_t>(value_size_));
}
Status CuckooTableBuilder::MakeHashTable(std::vector<CuckooBucket>* buckets) {
buckets->resize(
static_cast<size_t>(hash_table_size_ + cuckoo_block_size_ - 1));
uint32_t make_space_for_key_call_id = 0;
for (uint32_t vector_idx = 0; vector_idx < num_entries_; vector_idx++) {
uint64_t bucket_id = 0;
bool bucket_found = false;
autovector<uint64_t> hash_vals;
Slice user_key = GetUserKey(vector_idx);
for (uint32_t hash_cnt = 0; hash_cnt < num_hash_func_ && !bucket_found;
++hash_cnt) {
uint64_t hash_val =
CuckooHash(user_key, hash_cnt, use_module_hash_, hash_table_size_,
identity_as_first_hash_, get_slice_hash_);
// If there is a collision, check next cuckoo_block_size_ locations for
// empty locations. While checking, if we reach end of the hash table,
// stop searching and proceed for next hash function.
for (uint32_t block_idx = 0; block_idx < cuckoo_block_size_;
++block_idx, ++hash_val) {
if ((*buckets)[static_cast<size_t>(hash_val)].vector_idx ==
kMaxVectorIdx) {
bucket_id = hash_val;
bucket_found = true;
break;
} else {
if (ucomp_->Compare(
user_key, GetUserKey((*buckets)[static_cast<size_t>(hash_val)]
.vector_idx)) == 0) {
return Status::NotSupported("Same key is being inserted again.");
}
hash_vals.push_back(hash_val);
}
}
}
while (!bucket_found &&
!MakeSpaceForKey(hash_vals, ++make_space_for_key_call_id, buckets,
&bucket_id)) {
// Rehash by increashing number of hash tables.
if (num_hash_func_ >= max_num_hash_func_) {
return Status::NotSupported("Too many collisions. Unable to hash.");
}
// We don't really need to rehash the entire table because old hashes are
// still valid and we only increased the number of hash functions.
uint64_t hash_val = CuckooHash(user_key, num_hash_func_, use_module_hash_,
hash_table_size_, identity_as_first_hash_,
get_slice_hash_);
++num_hash_func_;
for (uint32_t block_idx = 0; block_idx < cuckoo_block_size_;
++block_idx, ++hash_val) {
if ((*buckets)[static_cast<size_t>(hash_val)].vector_idx ==
kMaxVectorIdx) {
bucket_found = true;
bucket_id = hash_val;
break;
} else {
hash_vals.push_back(hash_val);
}
}
}
(*buckets)[static_cast<size_t>(bucket_id)].vector_idx = vector_idx;
}
return Status::OK();
}
Status CuckooTableBuilder::Finish() {
assert(!closed_);
closed_ = true;
std::vector<CuckooBucket> buckets;
std::string unused_bucket;
if (num_entries_ > 0) {
// Calculate the real hash size if module hash is enabled.
if (use_module_hash_) {
hash_table_size_ =
static_cast<uint64_t>(num_entries_ / max_hash_table_ratio_);
}
status_ = MakeHashTable(&buckets);
if (!status_.ok()) {
return status_;
}
// Determine unused_user_key to fill empty buckets.
std::string unused_user_key = smallest_user_key_;
int curr_pos = static_cast<int>(unused_user_key.size()) - 1;
while (curr_pos >= 0) {
--unused_user_key[curr_pos];
if (Slice(unused_user_key).compare(smallest_user_key_) < 0) {
break;
}
--curr_pos;
}
if (curr_pos < 0) {
// Try using the largest key to identify an unused key.
unused_user_key = largest_user_key_;
curr_pos = static_cast<int>(unused_user_key.size()) - 1;
while (curr_pos >= 0) {
++unused_user_key[curr_pos];
if (Slice(unused_user_key).compare(largest_user_key_) > 0) {
break;
}
--curr_pos;
}
}
if (curr_pos < 0) {
return Status::Corruption("Unable to find unused key");
}
if (is_last_level_file_) {
unused_bucket = unused_user_key;
} else {
ParsedInternalKey ikey(unused_user_key, 0, kTypeValue);
AppendInternalKey(&unused_bucket, ikey);
}
}
properties_.num_entries = num_entries_;
properties_.num_deletions = num_entries_ - num_values_;
properties_.fixed_key_len = key_size_;
properties_.user_collected_properties[CuckooTablePropertyNames::kValueLength]
.assign(reinterpret_cast<const char*>(&value_size_), sizeof(value_size_));
uint64_t bucket_size = key_size_ + value_size_;
unused_bucket.resize(static_cast<size_t>(bucket_size), 'a');
// Write the table.
uint32_t num_added = 0;
for (auto& bucket : buckets) {
if (bucket.vector_idx == kMaxVectorIdx) {
io_status_ = file_->Append(Slice(unused_bucket));
} else {
++num_added;
io_status_ = file_->Append(GetKey(bucket.vector_idx));
if (io_status_.ok()) {
if (value_size_ > 0) {
io_status_ = file_->Append(GetValue(bucket.vector_idx));
}
}
}
if (!io_status_.ok()) {
status_ = io_status_;
return status_;
}
}
assert(num_added == NumEntries());
properties_.raw_key_size = num_added * properties_.fixed_key_len;
properties_.raw_value_size = num_added * value_size_;
uint64_t offset = buckets.size() * bucket_size;
properties_.data_size = offset;
unused_bucket.resize(static_cast<size_t>(properties_.fixed_key_len));
properties_.user_collected_properties[CuckooTablePropertyNames::kEmptyKey] =
unused_bucket;
properties_.user_collected_properties[CuckooTablePropertyNames::kNumHashFunc]
.assign(reinterpret_cast<char*>(&num_hash_func_), sizeof(num_hash_func_));
properties_
.user_collected_properties[CuckooTablePropertyNames::kHashTableSize]
.assign(reinterpret_cast<const char*>(&hash_table_size_),
sizeof(hash_table_size_));
properties_.user_collected_properties[CuckooTablePropertyNames::kIsLastLevel]
.assign(reinterpret_cast<const char*>(&is_last_level_file_),
sizeof(is_last_level_file_));
properties_
.user_collected_properties[CuckooTablePropertyNames::kCuckooBlockSize]
.assign(reinterpret_cast<const char*>(&cuckoo_block_size_),
sizeof(cuckoo_block_size_));
properties_
.user_collected_properties[CuckooTablePropertyNames::kIdentityAsFirstHash]
.assign(reinterpret_cast<const char*>(&identity_as_first_hash_),
sizeof(identity_as_first_hash_));
properties_
.user_collected_properties[CuckooTablePropertyNames::kUseModuleHash]
.assign(reinterpret_cast<const char*>(&use_module_hash_),
sizeof(use_module_hash_));
uint32_t user_key_len = static_cast<uint32_t>(smallest_user_key_.size());
properties_
.user_collected_properties[CuckooTablePropertyNames::kUserKeyLength]
.assign(reinterpret_cast<const char*>(&user_key_len),
sizeof(user_key_len));
// Write meta blocks.
MetaIndexBuilder meta_index_builder;
PropertyBlockBuilder property_block_builder;
property_block_builder.AddTableProperty(properties_);
property_block_builder.Add(properties_.user_collected_properties);
Slice property_block = property_block_builder.Finish();
BlockHandle property_block_handle;
property_block_handle.set_offset(offset);
property_block_handle.set_size(property_block.size());
io_status_ = file_->Append(property_block);
offset += property_block.size();
if (!io_status_.ok()) {
status_ = io_status_;
return status_;
}
meta_index_builder.Add(kPropertiesBlockName, property_block_handle);
Slice meta_index_block = meta_index_builder.Finish();
BlockHandle meta_index_block_handle;
meta_index_block_handle.set_offset(offset);
meta_index_block_handle.set_size(meta_index_block.size());
io_status_ = file_->Append(meta_index_block);
if (!io_status_.ok()) {
status_ = io_status_;
return status_;
}
FooterBuilder footer;
footer.Build(kCuckooTableMagicNumber, /* format_version */ 1, offset,
kNoChecksum, meta_index_block_handle);
io_status_ = file_->Append(footer.GetSlice());
status_ = io_status_;
return status_;
}
void CuckooTableBuilder::Abandon() {
assert(!closed_);
closed_ = true;
}
uint64_t CuckooTableBuilder::NumEntries() const { return num_entries_; }
uint64_t CuckooTableBuilder::FileSize() const {
if (closed_) {
return file_->GetFileSize();
} else if (num_entries_ == 0) {
return 0;
}
if (use_module_hash_) {
return static_cast<uint64_t>((key_size_ + value_size_) * num_entries_ /
max_hash_table_ratio_);
} else {
// Account for buckets being a power of two.
// As elements are added, file size remains constant for a while and
// doubles its size. Since compaction algorithm stops adding elements
// only after it exceeds the file limit, we account for the extra element
// being added here.
uint64_t expected_hash_table_size = hash_table_size_;
if (expected_hash_table_size < (num_entries_ + 1) / max_hash_table_ratio_) {
expected_hash_table_size *= 2;
}
return (key_size_ + value_size_) * expected_hash_table_size - 1;
}
}
// This method is invoked when there is no place to insert the target key.
// It searches for a set of elements that can be moved to accommodate target
// key. The search is a BFS graph traversal with first level (hash_vals)
// being all the buckets target key could go to.
// Then, from each node (curr_node), we find all the buckets that curr_node
// could go to. They form the children of curr_node in the tree.
// We continue the traversal until we find an empty bucket, in which case, we
// move all elements along the path from first level to this empty bucket, to
// make space for target key which is inserted at first level (*bucket_id).
// If tree depth exceedes max depth, we return false indicating failure.
bool CuckooTableBuilder::MakeSpaceForKey(
const autovector<uint64_t>& hash_vals,
const uint32_t make_space_for_key_call_id,
std::vector<CuckooBucket>* buckets, uint64_t* bucket_id) {
struct CuckooNode {
uint64_t bucket_id;
uint32_t depth;
uint32_t parent_pos;
CuckooNode(uint64_t _bucket_id, uint32_t _depth, int _parent_pos)
: bucket_id(_bucket_id), depth(_depth), parent_pos(_parent_pos) {}
};
// This is BFS search tree that is stored simply as a vector.
// Each node stores the index of parent node in the vector.
std::vector<CuckooNode> tree;
// We want to identify already visited buckets in the current method call so
// that we don't add same buckets again for exploration in the tree.
// We do this by maintaining a count of current method call in
// make_space_for_key_call_id, which acts as a unique id for this invocation
// of the method. We store this number into the nodes that we explore in
// current method call.
// It is unlikely for the increment operation to overflow because the maximum
// no. of times this will be called is <= max_num_hash_func_ + num_entries_.
for (uint32_t hash_cnt = 0; hash_cnt < num_hash_func_; ++hash_cnt) {
uint64_t bid = hash_vals[hash_cnt];
(*buckets)[static_cast<size_t>(bid)].make_space_for_key_call_id =
make_space_for_key_call_id;
tree.push_back(CuckooNode(bid, 0, 0));
}
bool null_found = false;
uint32_t curr_pos = 0;
while (!null_found && curr_pos < tree.size()) {
CuckooNode& curr_node = tree[curr_pos];
uint32_t curr_depth = curr_node.depth;
if (curr_depth >= max_search_depth_) {
break;
}
CuckooBucket& curr_bucket =
(*buckets)[static_cast<size_t>(curr_node.bucket_id)];
for (uint32_t hash_cnt = 0; hash_cnt < num_hash_func_ && !null_found;
++hash_cnt) {
uint64_t child_bucket_id = CuckooHash(
GetUserKey(curr_bucket.vector_idx), hash_cnt, use_module_hash_,
hash_table_size_, identity_as_first_hash_, get_slice_hash_);
// Iterate inside Cuckoo Block.
for (uint32_t block_idx = 0; block_idx < cuckoo_block_size_;
++block_idx, ++child_bucket_id) {
if ((*buckets)[static_cast<size_t>(child_bucket_id)]
.make_space_for_key_call_id == make_space_for_key_call_id) {
continue;
}
(*buckets)[static_cast<size_t>(child_bucket_id)]
.make_space_for_key_call_id = make_space_for_key_call_id;
tree.push_back(CuckooNode(child_bucket_id, curr_depth + 1, curr_pos));
if ((*buckets)[static_cast<size_t>(child_bucket_id)].vector_idx ==
kMaxVectorIdx) {
null_found = true;
break;
}
}
}
++curr_pos;
}
if (null_found) {
// There is an empty node in tree.back(). Now, traverse the path from this
// empty node to top of the tree and at every node in the path, replace
// child with the parent. Stop when first level is reached in the tree
// (happens when 0 <= bucket_to_replace_pos < num_hash_func_) and return
// this location in first level for target key to be inserted.
uint32_t bucket_to_replace_pos = static_cast<uint32_t>(tree.size()) - 1;
while (bucket_to_replace_pos >= num_hash_func_) {
CuckooNode& curr_node = tree[bucket_to_replace_pos];
(*buckets)[static_cast<size_t>(curr_node.bucket_id)] =
(*buckets)[static_cast<size_t>(tree[curr_node.parent_pos].bucket_id)];
bucket_to_replace_pos = curr_node.parent_pos;
}
*bucket_id = tree[bucket_to_replace_pos].bucket_id;
}
return null_found;
}
std::string CuckooTableBuilder::GetFileChecksum() const {
if (file_ != nullptr) {
return file_->GetFileChecksum();
} else {
return kUnknownFileChecksum;
}
}
const char* CuckooTableBuilder::GetFileChecksumFuncName() const {
if (file_ != nullptr) {
return file_->GetFileChecksumFuncName();
} else {
return kUnknownFileChecksumFuncName;
}
}
} // namespace ROCKSDB_NAMESPACE
#endif // ROCKSDB_LITE
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