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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
#ifndef ROCKSDB_LITE
#include <string>
#include <vector>
#include "rocksdb/comparator.h"
#include "rocksdb/db.h"
#include "rocksdb/utilities/stackable_db.h"
namespace ROCKSDB_NAMESPACE {
class Transaction;
// Database with Transaction support.
//
// See optimistic_transaction.h and examples/transaction_example.cc
// Options to use when starting an Optimistic Transaction
struct OptimisticTransactionOptions {
// Setting set_snapshot=true is the same as calling SetSnapshot().
bool set_snapshot = false;
// Should be set if the DB has a non-default comparator.
// See comment in WriteBatchWithIndex constructor.
const Comparator* cmp = BytewiseComparator();
};
enum class OccValidationPolicy {
// Validate serially at commit stage, AFTER entering the write-group.
// Isolation validation is processed single-threaded(since in the
// write-group).
// May suffer from high mutex contention, as per this link:
// https://github.com/facebook/rocksdb/issues/4402
kValidateSerial = 0,
// Validate parallelly before commit stage, BEFORE entering the write-group to
// reduce mutex contention. Each txn acquires locks for its write-set
// records in some well-defined order.
kValidateParallel = 1
};
struct OptimisticTransactionDBOptions {
OccValidationPolicy validate_policy = OccValidationPolicy::kValidateParallel;
// works only if validate_policy == OccValidationPolicy::kValidateParallel
uint32_t occ_lock_buckets = (1 << 20);
};
class OptimisticTransactionDB : public StackableDB {
public:
// Open an OptimisticTransactionDB similar to DB::Open().
static Status Open(const Options& options, const std::string& dbname,
OptimisticTransactionDB** dbptr);
static Status Open(const DBOptions& db_options, const std::string& dbname,
const std::vector<ColumnFamilyDescriptor>& column_families,
std::vector<ColumnFamilyHandle*>* handles,
OptimisticTransactionDB** dbptr);
static Status Open(const DBOptions& db_options,
const OptimisticTransactionDBOptions& occ_options,
const std::string& dbname,
const std::vector<ColumnFamilyDescriptor>& column_families,
std::vector<ColumnFamilyHandle*>* handles,
OptimisticTransactionDB** dbptr);
virtual ~OptimisticTransactionDB() {}
// Starts a new Transaction.
//
// Caller is responsible for deleting the returned transaction when no
// longer needed.
//
// If old_txn is not null, BeginTransaction will reuse this Transaction
// handle instead of allocating a new one. This is an optimization to avoid
// extra allocations when repeatedly creating transactions.
virtual Transaction* BeginTransaction(
const WriteOptions& write_options,
const OptimisticTransactionOptions& txn_options =
OptimisticTransactionOptions(),
Transaction* old_txn = nullptr) = 0;
OptimisticTransactionDB(const OptimisticTransactionDB&) = delete;
void operator=(const OptimisticTransactionDB&) = delete;
protected:
// To Create an OptimisticTransactionDB, call Open()
explicit OptimisticTransactionDB(DB* db) : StackableDB(db) {}
};
} // namespace ROCKSDB_NAMESPACE
#endif // ROCKSDB_LITE
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