Las traducciones son generadas a través de traducción automática. En caso de conflicto entre la traducción y la version original de inglés, prevalecerá la version en inglés. # Paso 4: consultar las tablas en un libro mayor **importante** Aviso de fin del soporte: los clientes actuales podrán utilizar Amazon QLDB hasta que finalice el soporte, el 31 de julio de 2025. Para obtener más información, consulte [Migración de un registro de Amazon QLDB a Amazon Aurora](https://aws.amazon.com/blogs/database/migrate-an-amazon-qldb-ledger-to-amazon-aurora-postgresql/) PostgreSQL. Tras crear tablas en un libro mayor de Amazon QLDB y cargarlas con datos, puede ejecutar consultas para revisar los datos de registro del vehículo que acaba de insertar. QLDB emplea [PartiQL](ql-reference.md) como lenguaje de consulta y [Amazon Ion](ion.md) como modelo de datos orientado a documentos. PartiQL es un lenguaje de consulta de código abierto compatible con SQL que se ha ampliado para funcionar con Ion. PartiQL le permite insertar, consultar y administrar sus datos con operadores SQL conocidos. Amazon Ion es un superconjunto de JSON. Ion es un formato de datos de código abierto basado en documentos que le brinda la flexibilidad de almacenar y procesar datos estructurados, semiestructurados y anidados. En este paso, puede usar las instrucciones `SELECT` para leer los datos de las tablas del libro mayor `vehicle-registration`. **aviso** Cuando ejecuta una consulta en QLDB sin una búsqueda indexada, se invoca un escaneo completo de la tabla. PartiQL admite este tipo de consultas porque es compatible con SQL. Sin embargo, *no* ejecute escaneados de tablas para casos de uso de producción en QLDB. Los escaneos de tablas pueden provocar problemas de rendimiento en tablas grandes, como conflictos de concurrencia y tiempos de espera de las transacciones. Para evitar el escaneado de tablas, debe ejecutar las instrucciones con una cláusula de predicado `WHERE` usando un operador de *igualdad* en un campo indexado o en un ID de documento, por ejemplo `WHERE indexedField = 123` o `WHERE indexedField IN (456, 789)`. Para obtener más información, consulte [Optimización del rendimiento de las consultas](working.optimize.md). **Para consultar las tablas** 1. Utilice el siguiente programa (`find_vehicles.py`) para consultar todos los vehículos registrados a nombre de una persona en su libro mayor. ------ #### [ 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 logging import basicConfig, getLogger, INFO from pyqldbsamples.model.sample_data import get_document_ids, print_result, SampleData from pyqldbsamples.constants import Constants from pyqldbsamples.connect_to_ledger import create_qldb_driver logger = getLogger(__name__) basicConfig(level=INFO) def find_vehicles_for_owner(driver, gov_id): """ Find vehicles registered under a driver using their government ID. :type driver: :py:class:`pyqldb.driver.qldb_driver.QldbDriver` :param driver: An instance of the QldbDriver class. :type gov_id: str :param gov_id: The owner's government ID. """ document_ids = driver.execute_lambda(lambda executor: get_document_ids(executor, Constants.PERSON_TABLE_NAME, 'GovId', gov_id)) query = "SELECT Vehicle FROM Vehicle INNER JOIN VehicleRegistration AS r " \ "ON Vehicle.VIN = r.VIN WHERE r.Owners.PrimaryOwner.PersonId = ?" for ids in document_ids: cursor = driver.execute_lambda(lambda executor: executor.execute_statement(query, ids)) logger.info('List of Vehicles for owner with GovId: {}...'.format(gov_id)) print_result(cursor) def main(ledger_name=Constants.LEDGER_NAME): """ Find all vehicles registered under a person. """ try: with create_qldb_driver(ledger_name) as driver: # Find all vehicles registered under a person. gov_id = SampleData.PERSON[0]['GovId'] find_vehicles_for_owner(driver, gov_id) except Exception as e: logger.exception('Error getting vehicles for owner.') 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 logging import basicConfig, getLogger, INFO from pyqldbsamples.model.sample_data import get_document_ids, print_result, SampleData from pyqldbsamples.constants import Constants from pyqldbsamples.connect_to_ledger import create_qldb_session logger = getLogger(__name__) basicConfig(level=INFO) def find_vehicles_for_owner(transaction_executor, gov_id): """ Find vehicles registered under a driver using their government ID. :type transaction_executor: :py:class:`pyqldb.execution.executor.Executor` :param transaction_executor: An Executor object allowing for execution of statements within a transaction. :type gov_id: str :param gov_id: The owner's government ID. """ document_ids = get_document_ids(transaction_executor, Constants.PERSON_TABLE_NAME, 'GovId', gov_id) query = "SELECT Vehicle FROM Vehicle INNER JOIN VehicleRegistration AS r " \ "ON Vehicle.VIN = r.VIN WHERE r.Owners.PrimaryOwner.PersonId = ?" for ids in document_ids: cursor = transaction_executor.execute_statement(query, ids) logger.info('List of Vehicles for owner with GovId: {}...'.format(gov_id)) print_result(cursor) if __name__ == '__main__': """ Find all vehicles registered under a person. """ try: with create_qldb_session() as session: # Find all vehicles registered under a person. gov_id = SampleData.PERSON[0]['GovId'] session.execute_lambda(lambda executor: find_vehicles_for_owner(executor, gov_id), lambda retry_attempt: logger.info('Retrying due to OCC conflict...')) except Exception: logger.exception('Error getting vehicles for owner.') ``` ------ **nota** En primer lugar, este programa consulta la tabla `Person` del documento con `GovId LEWISR261LL` para obtener su campo de metadatos `id`. A continuación, utiliza el `id` de este documento como clave externa para consultar la tabla `VehicleRegistration` mediante `PrimaryOwner.PersonId`. También combina `VehicleRegistration` con la tabla `Vehicle` en el campo `VIN`. 1. Para ejecutar el programa, introduzca el siguiente comando. ``` python find_vehicles.py ``` Para obtener información sobre la modificación de los documentos en las tablas del libro mayor `vehicle-registration`, consulte [Paso 5: modificar los documentos de un libro mayor](getting-started.python.step-5.md).