步驟 6：檢視文件的修訂歷史記錄

檢視修訂歷史記錄

1. 使用下列程式 (QueryHistory.ts) 查詢具有 VIN VehicleRegistration的文件修訂歷史記錄1N4AL11D75C109151。

   /*
    * 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.
    */
   
   import { QldbDriver, Result, TransactionExecutor } from "amazon-qldb-driver-nodejs";
   import { dom } from "ion-js";
   
   import { getQldbDriver } from "./ConnectToLedger";
   import { VEHICLE_REGISTRATION } from "./model/SampleData";
   import { VEHICLE_REGISTRATION_TABLE_NAME } from "./qldb/Constants";
   import { prettyPrintResultList } from "./ScanTable";
   import { error, log } from "./qldb/LogUtil";
   import { getDocumentId } from "./qldb/Util";
   
   /**
    * Find previous primary owners for the given VIN in a single transaction.
    * @param txn The {@linkcode TransactionExecutor} for lambda execute.
    * @param vin The VIN to find previous primary owners for.
    * @returns Promise which fulfills with void.
    */
   async function previousPrimaryOwners(txn: TransactionExecutor, vin: string): Promise<void> {
       const documentId: string = await getDocumentId(txn, VEHICLE_REGISTRATION_TABLE_NAME, "VIN", vin);
       const todaysDate: Date = new Date();
       // set todaysDate back one minute to ensure end time is in the past
       // by the time the request reaches our backend
       todaysDate.setMinutes(todaysDate.getMinutes() - 1);
       const threeMonthsAgo: Date = new Date(todaysDate);
       threeMonthsAgo.setMonth(todaysDate.getMonth() - 3);
   
       const query: string =
           `SELECT data.Owners.PrimaryOwner, metadata.version FROM history ` +
           `(${VEHICLE_REGISTRATION_TABLE_NAME}, \`${threeMonthsAgo.toISOString()}\`, \`${todaysDate.toISOString()}\`) ` +
           `AS h WHERE h.metadata.id = ?`;
   
       await txn.execute(query, documentId).then((result: Result) => {
           log(`Querying the 'VehicleRegistration' table's history using VIN: ${vin}.`);
           const resultList: dom.Value[] = result.getResultList();
           prettyPrintResultList(resultList);
       });
   }
   
   /**
    * Query a table's history for a particular set of documents.
    * @returns Promise which fulfills with void.
    */
   const main = async function(): Promise<void> {
       try {
           const qldbDriver: QldbDriver = getQldbDriver();
           const vin: string = VEHICLE_REGISTRATION[0].VIN;
           await qldbDriver.executeLambda(async (txn: TransactionExecutor) => {
               await previousPrimaryOwners(txn, vin);
           });
       } catch (e) {
           error(`Unable to query history to find previous owners: ${e}`);
       }
   }
   
   if (require.main === module) {
       main();
   }

   注意

   • 您可以在下列語法歷史記錄函數中查詢內建 ，以檢視文件的修訂歷史記錄。

     SELECT * FROM history( table_name [, `start-time` [, `end-time` ] ] ) AS h
     [ WHERE h.metadata.id = 'id' ]

   • 開始時間和結束時間皆為選用。它們是 Amazon Ion 常值，可以用反引號表示 (`...`)。如需詳細資訊，請參閱在 Amazon QLDB 中使用 PartiQL 查詢離子。

   • 最佳實務是，使用日期範圍 （開始時間和結束時間) 和文件 ID () 來限定歷史記錄查詢metadata.id。QLDB 會在交易中處理SELECT查詢，這些查詢受到交易逾時限制的限制。

     QLDB 歷史記錄會依文件 ID 編製索引，此時您無法建立其他歷史記錄索引。包含開始時間和結束時間的歷史記錄查詢，可受益於日期範圍資格。

2. 若要執行轉載程式，請輸入下列命令。

   node dist/QueryHistory.js