trx.cpp

/* Copyright (c) 2021 Xie Meiyi(xiemeiyi@hust.edu.cn) and OceanBase and/or its affiliates. All rights reserved.
miniob is licensed under Mulan PSL v2.
You can use this software according to the terms and conditions of the Mulan PSL v2.
You may obtain a copy of Mulan PSL v2 at:
         http://license.coscl.org.cn/MulanPSL2
THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
See the Mulan PSL v2 for more details. */

//
// Created by Wangyunlai on 2021/5/24.
//

#include <atomic>

#include "storage/trx/trx.h"
#include "storage/common/table.h"
#include "storage/common/record_manager.h"
#include "storage/common/field_meta.h"
#include "common/log/log.h"

static const uint32_t DELETED_FLAG_BIT_MASK = 0x80000000;
static const uint32_t TRX_ID_BIT_MASK = 0x7FFFFFFF;

int32_t Trx::default_trx_id() {
  return 0;
}

int32_t Trx::next_trx_id() {
  static std::atomic<int32_t> trx_id;
  return ++trx_id;
}

const char *Trx::trx_field_name() {
  return "__trx";
}

AttrType Trx::trx_field_type() {
  return INTS;
}

int Trx::trx_field_len() {
  return sizeof(int32_t);
}

Trx::Trx() {
}

Trx::~Trx() {
}

RC Trx::insert_record(Table *table, Record *record) {
  RC rc = RC::SUCCESS;
  // 先校验是否以前是否存在过(应该不会存在) 
  Operation *old_oper = find_operation(table, record->rid);
  if (old_oper != nullptr) {
    return RC::GENERIC_ERROR; // error code
  }

  start_if_not_started();

  // 设置record中trx_field为当前的事务号
  // set_record_trx_id(table, record, trx_id_, false);
  // 记录到operations中
  insert_operation(table, Operation::Type::INSERT, record->rid);
  return rc;
}

RC Trx::delete_record(Table *table, Record *record) {
  RC rc = RC::SUCCESS;
  start_if_not_started();
  Operation *old_oper = find_operation(table, record->rid);
  if (old_oper != nullptr) {
    if (old_oper->type() == Operation::Type::INSERT) {
      delete_operation(table, record->rid);
      return RC::SUCCESS;
    } else {
      return RC::GENERIC_ERROR;
    }
  }
  set_record_trx_id(table, *record, trx_id_, true);
  insert_operation(table, Operation::Type::DELETE, record->rid);
  return rc;
}

void Trx::set_record_trx_id(Table *table, Record &record, int32_t trx_id, bool deleted) const {
  const FieldMeta *trx_field = table->table_meta().trx_field();
  int32_t *ptrx_id = (int32_t*)(record.data + trx_field->offset());
  if (deleted) {
    trx_id |= DELETED_FLAG_BIT_MASK;
  }
  *ptrx_id = trx_id;
}

void Trx::get_record_trx_id(Table *table, const Record &record, int32_t &trx_id, bool &deleted) {
  const FieldMeta *trx_field = table->table_meta().trx_field();
  int32_t trx = *(int32_t*)(record.data + trx_field->offset());
  trx_id = trx & TRX_ID_BIT_MASK;
  deleted = (trx & DELETED_FLAG_BIT_MASK) != 0;
}

Operation *Trx::find_operation(Table *table, const RID &rid) {
  std::unordered_map<Table *, OperationSet>::iterator table_operations_iter = operations_.find(table);
  if (table_operations_iter == operations_.end()) {
    return nullptr;
  }

  OperationSet & table_operations = table_operations_iter->second;
  Operation tmp(Operation::Type::UNDEFINED, rid);
  OperationSet::iterator operation_iter = table_operations.find(tmp);
  if (operation_iter == table_operations.end()) {
    return nullptr;
  }
  return const_cast<Operation *>(&(*operation_iter));
}

void Trx::insert_operation(Table *table, Operation::Type type, const RID &rid) {
  OperationSet & table_operations = operations_[table];
  table_operations.emplace(type, rid);
}

void Trx::delete_operation(Table *table, const RID &rid) {

  std::unordered_map<Table *, OperationSet>::iterator table_operations_iter = operations_.find(table);
  if (table_operations_iter == operations_.end()) {
    return ;
  }

  Operation tmp(Operation::Type::UNDEFINED, rid);
  table_operations_iter->second.erase(tmp);
}

RC Trx::commit() {
  RC rc = RC::SUCCESS;
  for (const auto &table_operations: operations_) {
    Table *table = table_operations.first;
    const OperationSet &operation_set = table_operations.second;
    for (const Operation &operation: operation_set) {

      RID rid;
      rid.page_num = operation.page_num();
      rid.slot_num = operation.slot_num();

      switch (operation.type()) {
        case Operation::Type::INSERT: {
          rc = table->commit_insert(this, rid);
          if (rc != RC::SUCCESS) {
            // handle rc
            LOG_ERROR("Failed to commit insert operation. rid=%d.%d, rc=%d:%s",
                      rid.page_num, rid.slot_num, rc, strrc(rc));
          }
        }
        break;
        case Operation::Type::DELETE: {
          rc = table->commit_delete(this, rid);
          if (rc != RC::SUCCESS) {
            // handle rc
            LOG_ERROR("Failed to commit delete operation. rid=%d.%d, rc=%d:%s",
                      rid.page_num, rid.slot_num, rc, strrc(rc));
          }
        }
        break;
        default: {
          LOG_PANIC("Unknown operation. type=%d", (int)operation.type());
        }
        break;
      }
    }
  }

  operations_.clear();
  trx_id_ = 0;
  return rc;
}

RC Trx::rollback() {
  RC rc = RC::SUCCESS;
  for (const auto &table_operations: operations_) {
    Table *table = table_operations.first;
    const OperationSet &operation_set = table_operations.second;
    for (const Operation &operation: operation_set) {

      RID rid;
      rid.page_num = operation.page_num();
      rid.slot_num = operation.slot_num();

      switch (operation.type()) {
        case Operation::Type::INSERT: {
          rc = table->rollback_insert(this, rid);
          if (rc != RC::SUCCESS) {
            // handle rc
            LOG_ERROR("Failed to rollback insert operation. rid=%d.%d, rc=%d:%s",
                      rid.page_num, rid.slot_num, rc, strrc(rc));
          }
        }
          break;
        case Operation::Type::DELETE: {
          rc = table->rollback_delete(this, rid);
          if (rc != RC::SUCCESS) {
            // handle rc
            LOG_ERROR("Failed to rollback delete operation. rid=%d.%d, rc=%d:%s",
                      rid.page_num, rid.slot_num, rc, strrc(rc));
          }
        }
          break;
        default: {
          LOG_PANIC("Unknown operation. type=%d", (int)operation.type());
        }
          break;
      }
    }
  }

  operations_.clear();
  trx_id_ = 0;
  return rc;
}

RC Trx::commit_insert(Table *table, Record &record) {
  set_record_trx_id(table, record, 0, false);
  return RC::SUCCESS;
}

RC Trx::rollback_delete(Table *table, Record &record) {
  set_record_trx_id(table, record, 0, false);
  return RC::SUCCESS;
}

bool Trx::is_visible(Table *table, const Record *record) {
  int32_t record_trx_id;
  bool record_deleted;
  get_record_trx_id(table, *record, record_trx_id, record_deleted);

  // 0 表示这条数据已经提交
  if (0 == record_trx_id || record_trx_id == trx_id_) {
    return !record_deleted;
  }

  return record_deleted; // 当前记录上面有事务号，说明是未提交数据，那么如果有删除标记的话，就表示是未提交的删除
}

void Trx::init_trx_info(Table *table, Record &record) {
  set_record_trx_id(table, record, trx_id_, false);
}

void Trx::start_if_not_started() {
  if (trx_id_ == 0) {
    trx_id_ = next_trx_id();
  }
}