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# 6단계: 문서의 개정 기록 보기
<a name="getting-started.python.step-6"></a>

**중요**  
지원 종료 알림: 기존 고객은 07/31/2025에 지원이 종료될 때까지 Amazon QLDB를 사용할 수 있습니다. 자세한 내용은 [Amazon QLDB 원장을 Amazon Aurora PostgreSQL로 마이그레이션](https://aws.amazon.com/blogs/database/migrate-an-amazon-qldb-ledger-to-amazon-aurora-postgresql/)을 참조하세요.

이전 단계에서 차량의 등록 데이터를 수정한 후 등록된 모든 소유자의 기록과 기타 업데이트된 필드를 쿼리할 수 있습니다. 이 단계에서는 `vehicle-registration` 원장의 `VehicleRegistration` 테이블에 있는 문서의 개정 기록을 쿼리합니다.

**개정 기록을 보려면**

1. 다음 프로그램(`query_history.py`)을 사용하여 VIN `1N4AL11D75C109151`로 `VehicleRegistration` 문서의 개정 기록을 쿼리합니다.

------
#### [ 3.x ]

   ```
   # Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
   # SPDX-License-Identifier: MIT-0
   #
   # Permission is hereby granted, free of charge, to any person obtaining a copy of this
   # software and associated documentation files (the "Software"), to deal in the Software
   # without restriction, including without limitation the rights to use, copy, modify,
   # merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
   # permit persons to whom the Software is furnished to do so.
   #
   # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
   # INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
   # PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
   # HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
   # OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
   # SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   #
   # This code expects that you have AWS credentials setup per:
   # https://boto3.amazonaws.com/v1/documentation/api/latest/guide/quickstart.html
   from datetime import datetime, timedelta
   from logging import basicConfig, getLogger, INFO
   
   from pyqldbsamples.model.sample_data import print_result, get_document_ids, SampleData
   from pyqldbsamples.constants import Constants
   from pyqldbsamples.connect_to_ledger import create_qldb_driver
   
   logger = getLogger(__name__)
   basicConfig(level=INFO)
   
   
   def format_date_time(date_time):
       """
       Format the given date time to a string.
   
       :type date_time: :py:class:`datetime.datetime`
       :param date_time: The date time to format.
   
       :rtype: str
       :return: The formatted date time.
       """
       return date_time.strftime('`%Y-%m-%dT%H:%M:%S.%fZ`')
   
   
   def previous_primary_owners(driver, vin):
       """
       Find previous primary owners for the given VIN in a single transaction.
       In this example, query the `VehicleRegistration` history table to find all previous primary owners for a VIN.
   
       :type driver: :py:class:`pyqldb.driver.qldb_driver.QldbDriver`
       :param driver: An instance of the QldbDriver class.
   
       :type vin: str
       :param vin: VIN to find previous primary owners for.
       """
       person_ids = driver.execute_lambda(lambda executor: get_document_ids(executor,
                                                                            Constants.VEHICLE_REGISTRATION_TABLE_NAME,
                                                                            'VIN', vin))
   
       todays_date = datetime.utcnow() - timedelta(seconds=1)
       three_months_ago = todays_date - timedelta(days=90)
       query = 'SELECT data.Owners.PrimaryOwner, metadata.version FROM history({}, {}, {}) AS h WHERE h.metadata.id = ?'.\
           format(Constants.VEHICLE_REGISTRATION_TABLE_NAME, format_date_time(three_months_ago),
                  format_date_time(todays_date))
   
       for ids in person_ids:
           logger.info("Querying the 'VehicleRegistration' table's history using VIN: {}.".format(vin))
           cursor = driver.execute_lambda(lambda executor: executor.execute_statement(query, ids))
           if not (print_result(cursor)) > 0:
               logger.info('No modification history found within the given time frame for document ID: {}'.format(ids))
   
   
   def main(ledger_name=Constants.LEDGER_NAME):
       """
       Query a table's history for a particular set of documents.
       """
       try:
           with create_qldb_driver(ledger_name) as driver:
               vin = SampleData.VEHICLE_REGISTRATION[0]['VIN']
               previous_primary_owners(driver, vin)
               logger.info('Successfully queried history.')
       except Exception as e:
           logger.exception('Unable to query history to find previous owners.')
           raise e
   
   
   if __name__ == '__main__':
       main()
   ```

------
#### [ 2.x ]

   ```
   # Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
   # SPDX-License-Identifier: MIT-0
   #
   # Permission is hereby granted, free of charge, to any person obtaining a copy of this
   # software and associated documentation files (the "Software"), to deal in the Software
   # without restriction, including without limitation the rights to use, copy, modify,
   # merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
   # permit persons to whom the Software is furnished to do so.
   #
   # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
   # INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
   # PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
   # HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
   # OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
   # SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   #
   # This code expects that you have AWS credentials setup per:
   # https://boto3.amazonaws.com/v1/documentation/api/latest/guide/quickstart.html
   from datetime import datetime, timedelta
   from logging import basicConfig, getLogger, INFO
   
   from pyqldbsamples.model.sample_data import print_result, get_document_ids, SampleData
   from pyqldbsamples.constants import Constants
   from pyqldbsamples.connect_to_ledger import create_qldb_session
   
   logger = getLogger(__name__)
   basicConfig(level=INFO)
   
   
   def format_date_time(date_time):
       """
       Format the given date time to a string.
   
       :type date_time: :py:class:`datetime.datetime`
       :param date_time: The date time to format.
   
       :rtype: str
       :return: The formatted date time.
       """
       return date_time.strftime('`%Y-%m-%dT%H:%M:%S.%fZ`')
   
   
   def previous_primary_owners(transaction_executor, vin):
       """
       Find previous primary owners for the given VIN in a single transaction.
       In this example, query the `VehicleRegistration` history table to find all previous primary owners for a VIN.
   
       :type transaction_executor: :py:class:`pyqldb.execution.executor.Executor`
       :param transaction_executor: An Executor object allowing for execution of statements within a transaction.
   
       :type vin: str
       :param vin: VIN to find previous primary owners for.
       """
       person_ids = get_document_ids(transaction_executor, Constants.VEHICLE_REGISTRATION_TABLE_NAME, 'VIN', vin)
   
       todays_date = datetime.utcnow() - timedelta(seconds=1)
       three_months_ago = todays_date - timedelta(days=90)
       query = 'SELECT data.Owners.PrimaryOwner, metadata.version FROM history({}, {}, {}) AS h WHERE h.metadata.id = ?'.\
           format(Constants.VEHICLE_REGISTRATION_TABLE_NAME, format_date_time(three_months_ago),
                  format_date_time(todays_date))
   
       for ids in person_ids:
           logger.info("Querying the 'VehicleRegistration' table's history using VIN: {}.".format(vin))
           cursor = transaction_executor.execute_statement(query, ids)
           if not (print_result(cursor)) > 0:
               logger.info('No modification history found within the given time frame for document ID: {}'.format(ids))
   
   
   if __name__ == '__main__':
       """
       Query a table's history for a particular set of documents.
       """
       try:
           with create_qldb_session() as session:
               vin = SampleData.VEHICLE_REGISTRATION[0]['VIN']
               session.execute_lambda(lambda lambda_executor: previous_primary_owners(lambda_executor, vin),
                                      lambda retry_attempt: logger.info('Retrying due to OCC conflict...'))
               logger.info('Successfully queried history.')
       except Exception:
           logger.exception('Unable to query history to find previous owners.')
   ```

------
**참고**  
다음 구문에 내장된 [기록 함수](working.history.md#working.history.function)를 쿼리하여 문서의 개정 기록을 볼 수 있습니다  

     ```
     SELECT * FROM history( table_name [, `start-time` [, `end-time` ] ] ) AS h
     [ WHERE h.metadata.id = 'id' ]
     ```
*시작 시간*과 *종료 시간*은 모두 선택 사항입니다. 이 값은 백틱(``...``)으로 표시할 수 있는 Amazon Ion 리터럴 값입니다. 자세한 내용은 [Amazon QLDB에서 PartiQL을 사용한 Ion 쿼리](ql-reference.query.md) 섹션을 참조하세요.
가장 좋은 방법은 날짜 범위(*시작 시간* 및 *종료 시간*)와 문서 ID(`metadata.id`)를 모두 사용하여 기록 쿼리를 한정하는 것입니다. QLDB는 트랜잭션에서 `SELECT` 쿼리를 처리하며, 이 쿼리에는 [트랜잭션 시간 초과 제한](limits.md#limits.fixed)이 적용됩니다.  
QLDB 기록은 문서 ID로 인덱싱되며, 이번에는 추가 기록 인덱스를 만들 수 없습니다. 시작 시간과 종료 시간을 포함하는 기록 쿼리는 날짜 범위 한정이라는 이점을 갖습니다.

1. 프로그램을 실행하려면 다음 명령을 입력합니다.

   ```
   python query_history.py
   ```

`vehicle-registration` 원장의 문서 개정을 암호화 방식으로 검증하려면 [7단계: 원장에 있는 문서 검증](getting-started.python.step-7.md)으로 진행하세요.