rocksdb/util/duplicate_detector.h

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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).
#pragma once
#include <cinttypes>
#include "util/set_comparator.h"
namespace rocksdb {
// During recovery if the memtable is flushed we cannot rely on its help on
// duplicate key detection and as key insert will not be attempted. This class
// will be used as a emulator of memtable to tell if insertion of a key/seq
// would have resulted in duplication.
class DuplicateDetector {
public:
explicit DuplicateDetector(DBImpl* db) : db_(db) {}
bool IsDuplicateKeySeq(uint32_t cf, const Slice& key, SequenceNumber seq) {
assert(seq >= batch_seq_);
if (batch_seq_ != seq) { // it is a new batch
keys_.clear();
}
batch_seq_ = seq;
CFKeys& cf_keys = keys_[cf];
if (cf_keys.size() == 0) { // just inserted
InitWithComp(cf);
}
auto it = cf_keys.insert(key);
if (it.second == false) { // second is false if a element already existed.
keys_.clear();
InitWithComp(cf);
keys_[cf].insert(key);
return true;
}
return false;
}
private:
SequenceNumber batch_seq_ = 0;
DBImpl* db_;
using CFKeys = std::set<Slice, SetComparator>;
std::map<uint32_t, CFKeys> keys_;
void InitWithComp(const uint32_t cf) {
auto h = db_->GetColumnFamilyHandle(cf);
if (!h) {
// TODO(myabandeh): This is not a concern in MyRocks as drop cf is not
// implemented yet. When it does, we should return proper error instead
// of throwing exception.
ROCKS_LOG_FATAL(
db_->immutable_db_options().info_log,
"Recovering an entry from the dropped column family %" PRIu32
". WAL must must have been emptied before dropping the column "
"family", cf);
#ifndef ROCKSDB_LITE
throw std::runtime_error(
"Recovering an entry from a dropped column family. "
"WAL must must have been flushed before dropping the column "
"family");
#endif
return;
}
auto cmp = h->GetComparator();
keys_[cf] = CFKeys(SetComparator(cmp));
}
};
} // namespace rocksdb