Paso 4: Consultar las tablas de un libro mayor - Amazon Quantum Ledger Database (Amazon QLDB)

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Paso 4: Consultar las tablas de un libro mayor

Después de 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. UsarUsePartiQLcomo lenguaje de consulta yAmazon Ioncomo su modelo de datos orientado a documentos.

PartiQL es un lenguaje de consulta de código abierto compatible con SQL que se ha ampliado para que funcione con Ion. Con PartiQL, puede 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, utiliceSELECTinstrucciones para leer datos de las tablas devehicle-registrationlibro mayor.

aviso

Cuando ejecuta una consulta en QLDB sin una búsqueda indexada, se invoca una exploración de tabla completa. PartiQL admite este tipo de consultas porque es compatible con SQL. Sin embargo,Don'tejecutar escaneos de tablas para casos de uso de producción en QLDB. Los análisis de tablas pueden provocar problemas de rendimiento en tablas grandes, incluidos conflictos de simultaneidad y tiempos de espera de transacciones.

Para evitar el análisis de tablas, debe ejecutar sentencias con unWHEREcláusula de predicado mediante unaigualdadoperador en un campo indexado o un ID de documento; por ejemplo,WHERE indexedField = 123oWHERE indexedField IN (456, 789). Para obtener más información, consulte Optimización del rendimiento de consultas.

Para consultar las tablas

  • Compile y ejecute el programa (FindVehicles.java) para consultar todos los vehículos registrados a nombre de una persona en su libro mayor.

    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. */ package software.amazon.qldb.tutorial; import java.io.IOException; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.amazon.ion.IonValue; import software.amazon.qldb.Result; import software.amazon.qldb.TransactionExecutor; import software.amazon.qldb.tutorial.model.Person; import software.amazon.qldb.tutorial.model.SampleData; /** * Find all vehicles registered under a person. * * This code expects that you have AWS credentials setup per: * http://docs.aws.amazon.com/java-sdk/latest/developer-guide/setup-credentials.html */ public final class FindVehicles { public static final Logger log = LoggerFactory.getLogger(FindVehicles.class); private FindVehicles() { } /** * Find vehicles registered under a driver using their government ID. * * @param txn * The {@link TransactionExecutor} for lambda execute. * @param govId * The government ID of the owner. * @throws IllegalStateException if failed to convert parameters into {@link IonValue}. */ public static void findVehiclesForOwner(final TransactionExecutor txn, final String govId) { try { final String documentId = Person.getDocumentIdByGovId(txn, govId); final String query = "SELECT v FROM Vehicle AS v INNER JOIN VehicleRegistration AS r " + "ON v.VIN = r.VIN WHERE r.Owners.PrimaryOwner.PersonId = ?"; final Result result = txn.execute(query, Constants.MAPPER.writeValueAsIonValue(documentId)); log.info("List of Vehicles for owner with GovId: {}...", govId); ScanTable.printDocuments(result); } catch (IOException ioe) { throw new IllegalStateException(ioe); } } public static void main(final String... args) { final Person person = SampleData.PEOPLE.get(0); ConnectToLedger.getDriver().execute(txn -> { findVehiclesForOwner(txn, person.getGovId()); }); } }
    1.x
    /* * Copyright 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. */ package software.amazon.qldb.tutorial; import java.io.IOException; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.amazon.ion.IonValue; import software.amazon.qldb.Result; import software.amazon.qldb.TransactionExecutor; import software.amazon.qldb.tutorial.model.Person; import software.amazon.qldb.tutorial.model.SampleData; /** * Find all vehicles registered under a person. * * This code expects that you have AWS credentials setup per: * http://docs.aws.amazon.com/java-sdk/latest/developer-guide/setup-credentials.html */ public final class FindVehicles { public static final Logger log = LoggerFactory.getLogger(FindVehicles.class); private FindVehicles() { } /** * Find vehicles registered under a driver using their government ID. * * @param txn * The {@link TransactionExecutor} for lambda execute. * @param govId * The government ID of the owner. * @throws IllegalStateException if failed to convert parameters into {@link IonValue}. */ public static void findVehiclesForOwner(final TransactionExecutor txn, final String govId) { try { final String documentId = Person.getDocumentIdByGovId(txn, govId); final String query = "SELECT v FROM Vehicle AS v INNER JOIN VehicleRegistration AS r " + "ON v.VIN = r.VIN WHERE r.Owners.PrimaryOwner.PersonId = ?"; final Result result = txn.execute(query, Constants.MAPPER.writeValueAsIonValue(documentId)); log.info("List of Vehicles for owner with GovId: {}...", govId); ScanTable.printDocuments(result); } catch (IOException ioe) { throw new IllegalStateException(ioe); } } public static void main(final String... args) { final Person person = SampleData.PEOPLE.get(0); ConnectToLedger.getDriver().execute(txn -> { findVehiclesForOwner(txn, person.getGovId()); }, (retryAttempt) -> log.info("Retrying due to OCC conflict...")); } }
    nota

    En primer lugar, este programa consulta elPersontabla para el documento conGovId LEWISR261LLpara conseguir suidcampo de metadatos.

    A continuación, utiliza este documentoidcomo clave externa para consultar elVehicleRegistrationmesa dePrimaryOwner.PersonId. También se uneVehicleRegistrationconVehiclemesa en laVIN.

Para obtener más información sobre la modificación de documentos en las tablas devehicle-registrationlibro mayor, consultePaso 5: Modificar documentos de un libro mayor.