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Paso 4: consultar las tablas en un libro mayor
Tras crear tablas en un QLDB libro mayor de Amazon y cargarlas con datos, puedes ejecutar consultas para revisar los datos de registro del vehículo que acabas de insertar. QLDButiliza PartiQL como lenguaje de consulta y Amazon Ion como modelo de datos orientado a documentos.
PartiQL es un lenguaje de consulta SQL compatible y de código abierto que se ha ampliado para funcionar con Ion. Con PartiQL, puede insertar, consultar y administrar sus datos con operadores conocidosSQL. Amazon Ion es un superconjunto deJSON. 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.
Cuando ejecutas una consulta QLDB sin una búsqueda indexada, se invoca un escaneo completo de la tabla. PartiQL admite este tipo de consultas porque es SQL compatible. Sin embargo, no ejecute escaneos de tablas para casos de uso de producción enQLDB. 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.
Para consultar las tablas
-
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.')
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.
-
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.
