Step 6: View the revision history for a document - Amazon Quantum Ledger Database (Amazon QLDB)

Step 6: View the revision history for a document

After modifying registration data for a vehicle in the previous step, you can query the history of all its registered owners and any other updated fields. In this step, you query the revision history of a document in the VehicleRegistration table in your vehicle-registration ledger.

To view the revision history
  1. Use the following program (query_history.py) to query the revision history of the VehicleRegistration document with VIN 1N4AL11D75C109151.

    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.')
    Note
    • You can view the revision history of a document by querying the built-in History function in the following syntax.

      SELECT * FROM history( table_name [, `start-time` [, `end-time` ] ] ) AS h [ WHERE h.metadata.id = 'id' ]
    • The start-time and end-time are both optional. They're Amazon Ion literal values that can be denoted with backticks (`...`). To learn more, see Querying Ion with PartiQL in Amazon QLDB.

    • As a best practice, qualify a history query with both a date range (start-time and end-time) and a document ID (metadata.id). QLDB processes SELECT queries in transactions, which are subject to a transaction timeout limit.

      QLDB history is indexed by document ID, and you can't create additional history indexes at this time. History queries that include a start time and end time gain the benefit of date range qualification.

  2. To run the program, enter the following command.

    python query_history.py

To cryptographically verify a document revision in the vehicle-registration ledger, proceed to Step 7: Verify a document in a ledger.