fork of https://github.com/oxigraph/rocksdb and https://github.com/facebook/rocksdb for nextgraph and oxigraph
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332 lines
11 KiB
332 lines
11 KiB
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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#ifndef ROCKSDB_LITE
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#include "table/cuckoo_table_builder.h"
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#include <assert.h>
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#include <algorithm>
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#include <string>
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#include <vector>
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#include "db/dbformat.h"
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#include "rocksdb/env.h"
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#include "rocksdb/table.h"
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#include "table/block_builder.h"
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#include "table/format.h"
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#include "table/meta_blocks.h"
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#include "util/autovector.h"
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#include "util/random.h"
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namespace rocksdb {
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const std::string CuckooTablePropertyNames::kEmptyBucket =
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"rocksdb.cuckoo.bucket.empty.bucket";
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const std::string CuckooTablePropertyNames::kNumHashTable =
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"rocksdb.cuckoo.hash.num";
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const std::string CuckooTablePropertyNames::kMaxNumBuckets =
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"rocksdb.cuckoo.bucket.maxnum";
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// Obtained by running echo rocksdb.table.cuckoo | sha1sum
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extern const uint64_t kCuckooTableMagicNumber = 0x926789d0c5f17873ull;
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CuckooTableBuilder::CuckooTableBuilder(
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WritableFile* file, unsigned int fixed_key_length,
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unsigned int fixed_value_length, double hash_table_ratio,
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unsigned int file_size, unsigned int max_num_hash_table,
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unsigned int max_search_depth,
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unsigned int (*GetSliceHashPtr)(const Slice&, unsigned int,
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unsigned int))
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: num_hash_table_(std::min((unsigned int) 4, max_num_hash_table)),
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file_(file),
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value_length_(fixed_value_length),
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bucket_size_(fixed_key_length + fixed_value_length),
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hash_table_ratio_(hash_table_ratio),
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max_num_buckets_(file_size / bucket_size_),
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max_num_hash_table_(max_num_hash_table),
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max_search_depth_(max_search_depth),
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buckets_(max_num_buckets_),
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GetSliceHash(GetSliceHashPtr) {
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// The bucket_size is currently not optimized for last level.
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// In last level, the bucket will not contain full key.
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// TODO(rbs): Find how we can determine if last level or not
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// before we start adding entries into the table.
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properties_.num_entries = 0;
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// Data is in a huge block.
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properties_.num_data_blocks = 1;
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properties_.index_size = 0;
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properties_.filter_size = 0;
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}
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CuckooTableBuilder::~CuckooTableBuilder() {
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}
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void CuckooTableBuilder::Add(const Slice& key, const Slice& value) {
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if (NumEntries() == max_num_buckets_) {
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status_ = Status::Corruption("Hash Table is full.");
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return;
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}
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unsigned int bucket_id;
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bool bucket_found = false;
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autovector<unsigned int> hash_vals;
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ParsedInternalKey ikey;
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if (!ParseInternalKey(key, &ikey)) {
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status_ = Status::Corruption("Unable to parse key into inernal key.");
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return;
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}
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Slice user_key = ikey.user_key;
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for (unsigned int hash_cnt = 0; hash_cnt < num_hash_table_; ++hash_cnt) {
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unsigned int hash_val = GetSliceHash(user_key, hash_cnt, max_num_buckets_);
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if (buckets_[hash_val].is_empty) {
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bucket_id = hash_val;
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bucket_found = true;
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break;
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} else {
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if (user_key.compare(ExtractUserKey(buckets_[hash_val].key)) == 0) {
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status_ = Status::Corruption("Same key is being inserted again.");
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return;
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}
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hash_vals.push_back(hash_val);
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}
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}
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while (!bucket_found && !MakeSpaceForKey(key, &bucket_id, hash_vals)) {
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// Rehash by increashing number of hash tables.
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if (num_hash_table_ >= max_num_hash_table_) {
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status_ = Status::Corruption("Too many collissions. Unable to hash.");
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return;
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}
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// We don't really need to rehash the entire table because old hashes are
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// still valid and we only increased the number of hash functions.
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unsigned int old_num_hash = num_hash_table_;
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num_hash_table_ = std::min(num_hash_table_ + 1, max_num_hash_table_);
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for (unsigned int i = old_num_hash; i < num_hash_table_; i++) {
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unsigned int hash_val = GetSliceHash(user_key, i, max_num_buckets_);
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if (buckets_[hash_val].is_empty) {
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bucket_found = true;
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bucket_id = hash_val;
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break;
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} else {
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hash_vals.push_back(hash_val);
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}
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}
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}
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buckets_[bucket_id].key = key;
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buckets_[bucket_id].value = value;
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buckets_[bucket_id].is_empty = false;
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if (ikey.sequence != 0) {
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// This is not a last level file.
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is_last_level_file_ = false;
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}
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properties_.num_entries++;
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// We assume that the keys are inserted in sorted order. To identify an
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// unused key, which will be used in filling empty buckets in the table,
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// we try to find gaps between successive keys inserted. This is done by
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// maintaining the previous key and comparing it with next key.
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if (unused_user_key_.empty()) {
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if (prev_key_.empty()) {
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prev_key_ = user_key.ToString();
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return;
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}
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std::string new_user_key = prev_key_;
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new_user_key.back()++;
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// We ignore carry-overs and check that it is larger than previous key.
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if ((new_user_key > prev_key_) &&
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(new_user_key < user_key.ToString())) {
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unused_user_key_ = new_user_key;
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} else {
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prev_key_ = user_key.ToString();
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}
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}
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}
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Status CuckooTableBuilder::status() const { return status_; }
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Status CuckooTableBuilder::Finish() {
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assert(!closed_);
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closed_ = true;
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if (unused_user_key_.empty()) {
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if (prev_key_.empty()) {
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return Status::Corruption("Unable to find unused key");
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}
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std::string new_user_key = prev_key_;
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new_user_key.back()++;
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// We ignore carry-overs and check that it is larger than previous key.
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if (new_user_key > prev_key_) {
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unused_user_key_ = new_user_key;
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} else {
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return Status::Corruption("Unable to find unused key");
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}
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}
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std::string unused_bucket;
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if (is_last_level_file_) {
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unused_bucket = unused_user_key_;
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} else {
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ParsedInternalKey ikey(unused_user_key_, 0, kTypeValue);
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AppendInternalKey(&unused_bucket, ikey);
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}
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properties_.fixed_key_len = unused_bucket.size();
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unsigned int bucket_size = unused_bucket.size() + value_length_;
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// Resize to bucket size.
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unused_bucket.resize(bucket_size, 'a');
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// Write the table.
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for (auto& bucket : buckets_) {
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Status s;
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if (bucket.is_empty) {
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s = file_->Append(Slice(unused_bucket));
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} else {
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if (is_last_level_file_) {
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Slice user_key = ExtractUserKey(bucket.key);
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s = file_->Append(user_key);
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if (s.ok()) {
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s = file_->Append(bucket.value);
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}
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} else {
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s = file_->Append(bucket.key);
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if (s.ok()) {
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s = file_->Append(bucket.value);
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}
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}
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}
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if (!s.ok()) {
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return s;
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}
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}
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unsigned int offset = buckets_.size() * bucket_size;
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properties_.user_collected_properties[
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CuckooTablePropertyNames::kEmptyBucket] = unused_bucket;
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properties_.user_collected_properties[
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CuckooTablePropertyNames::kNumHashTable] = std::to_string(num_hash_table_);
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PutVarint32(&properties_.user_collected_properties[
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CuckooTablePropertyNames::kMaxNumBuckets], max_num_buckets_);
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// Write meta blocks.
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MetaIndexBuilder meta_index_builer;
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PropertyBlockBuilder property_block_builder;
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property_block_builder.AddTableProperty(properties_);
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property_block_builder.Add(properties_.user_collected_properties);
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Slice property_block = property_block_builder.Finish();
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BlockHandle property_block_handle;
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property_block_handle.set_offset(offset);
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property_block_handle.set_size(property_block.size());
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Status s = file_->Append(property_block);
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offset += property_block.size();
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if (!s.ok()) {
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return s;
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}
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meta_index_builer.Add(kPropertiesBlock, property_block_handle);
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Slice meta_index_block = meta_index_builer.Finish();
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BlockHandle meta_index_block_handle;
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meta_index_block_handle.set_offset(offset);
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meta_index_block_handle.set_size(meta_index_block.size());
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s = file_->Append(meta_index_block);
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if (!s.ok()) {
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return s;
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}
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Footer footer(kCuckooTableMagicNumber);
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footer.set_metaindex_handle(meta_index_block_handle);
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footer.set_index_handle(BlockHandle::NullBlockHandle());
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std::string footer_encoding;
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footer.EncodeTo(&footer_encoding);
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s = file_->Append(footer_encoding);
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return s;
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}
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void CuckooTableBuilder::Abandon() {
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assert(!closed_);
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closed_ = true;
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}
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uint64_t CuckooTableBuilder::NumEntries() const {
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return properties_.num_entries;
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}
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uint64_t CuckooTableBuilder::FileSize() const {
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if (closed_) {
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return file_->GetFileSize();
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} else {
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// This is not the actual size of the file as we need to account for
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// hash table ratio. This returns the size of filled buckets in the table
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// scaled up by a factor of 1/hash table ratio.
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return (properties_.num_entries * bucket_size_) / hash_table_ratio_;
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}
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}
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bool CuckooTableBuilder::MakeSpaceForKey(const Slice& key,
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unsigned int *bucket_id, autovector<unsigned int> hash_vals) {
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struct CuckooNode {
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unsigned int bucket_id;
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unsigned int depth;
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int parent_pos;
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CuckooNode(unsigned int bucket_id, unsigned int depth, int parent_pos)
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: bucket_id(bucket_id), depth(depth), parent_pos(parent_pos) {}
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};
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// This is BFS search tree that is stored simply as a vector.
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// Each node stores the index of parent node in the vector.
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std::vector<CuckooNode> tree;
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// This is a very bad way to keep track of visited nodes.
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// TODO(rbs): Change this by adding a 'GetKeyPathId' field to the bucket
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// and use it to track visited nodes.
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std::vector<bool> buckets_visited(max_num_buckets_, false);
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for (unsigned int hash_cnt = 0; hash_cnt < num_hash_table_; ++hash_cnt) {
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unsigned int bucket_id = hash_vals[hash_cnt];
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buckets_visited[bucket_id] = true;
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tree.push_back(CuckooNode(bucket_id, 0, -1));
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}
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bool null_found = false;
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unsigned int curr_pos = 0;
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while (!null_found && curr_pos < tree.size()) {
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CuckooNode& curr_node = tree[curr_pos];
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if (curr_node.depth >= max_search_depth_) {
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break;
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}
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CuckooBucket& curr_bucket = buckets_[curr_node.bucket_id];
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for (unsigned int hash_cnt = 0; hash_cnt < num_hash_table_; ++hash_cnt) {
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unsigned int child_bucket_id = GetSliceHash(
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ExtractUserKey(curr_bucket.key), hash_cnt, max_num_buckets_);
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if (child_bucket_id == curr_node.bucket_id) {
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continue;
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}
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if (buckets_visited[child_bucket_id]) {
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continue;
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}
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buckets_visited[child_bucket_id] = true;
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tree.push_back(CuckooNode(child_bucket_id, curr_node.depth + 1,
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curr_pos));
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if (buckets_[child_bucket_id].is_empty) {
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null_found = true;
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break;
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}
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}
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++curr_pos;
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}
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if (null_found) {
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int bucket_to_replace_pos = tree.size()-1;
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while (bucket_to_replace_pos >= 0) {
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CuckooNode& curr_node = tree[bucket_to_replace_pos];
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if (curr_node.parent_pos != -1) {
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buckets_[curr_node.bucket_id] = buckets_[curr_node.parent_pos];
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bucket_to_replace_pos = curr_node.parent_pos;
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} else {
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*bucket_id = curr_node.bucket_id;
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return true;
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}
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}
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return true;
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} else {
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return false;
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}
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}
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} // namespace rocksdb
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#endif // ROCKSDB_LITE
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