Langkah 4: Cari tabel dalam buku besar

Setelah membuat tabel di buku besar Amazon QLDB dan memuatnya dengan data, Anda dapat menjalankan kueri untuk meninjau data registrasi kendaraan yang baru saja Anda masukkan. QLDB menggunakan PartiQL sebagai bahasa kueri dan Amazon Ion sebagai model data berorientasi dokumen.

PartiQL adalah open-source, bahasa query SQL-kompatibel yang telah diperluas untuk bekerja dengan Ion. Dengan PartiQL, Anda dapat memasukkan, query, dan mengelola data Anda dengan operator SQL akrab. Amazon Ion adalah superset dari JSON. Ion adalah open-source, format data berbasis dokumen yang memberi Anda fleksibilitas menyimpan dan memproses data terstruktur, semistruktural, dan bersarang.

Pada langkah ini, Anda menggunakanSELECT pernyataan untuk membaca data dari tabel divehicle-registration buku besar.

Awas

Ketika Anda menjalankan query di QLDB tanpa pencarian diindeks, memanggil scan tabel penuh. PartiQL mendukung query tersebut karena SQL kompatibel. Namun, jangan jalankan pemindaian tabel untuk kasus penggunaan produksi di QLDB. Pemindaian tabel dapat menyebabkan masalah kinerja pada tabel besar, termasuk konflik konkurensi dan batas waktu transaksi.

Untuk menghindari pemindaian tabel, Anda harus menjalankan pernyataan dengan klausaWHERE predikat menggunakan operator kesetaraan pada bidang yang diindeks atau ID dokumen; misalnya,WHERE indexedField = 123 atauWHERE indexedField IN (456, 789). Untuk informasi selengkapnya, lihat Mengoptimalkan kinerja kueri.

Untuk query tabel

1. Gunakan program berikut (find_vehicles.py) untuk meminta semua kendaraan yang terdaftar di bawah seseorang di buku besar Anda.

   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.')

   catatan

   Pertama, program ini queryPerson tabel untuk dokumen denganGovId LEWISR261LL untuk mendapatkan bidangid metadata.

   Kemudian, menggunakan dokumen iniid sebagai kunci asing untuk queryVehicleRegistration tabel olehPrimaryOwner.PersonId. Ini juga bergabungVehicleRegistration denganVehicle meja diVIN lapangan.

2. Untuk menjalankan program, masukkan perintah berikut.

   python find_vehicles.py

Untuk mempelajari tentang memodifikasi dokumen dalam tabel divehicle-registration buku besar, lihatLangkah 5: Memodifikasi dokumen dalam buku besar.