Step 6: View the revision history for a
document
After modifying registration data for a vehicle in the previous step, you can query the
history of all its registered owners and any other updated fields. In this step, you query the
revision history of a document in the VehicleRegistration
table in your
vehicle-registration
ledger.
To view the revision history
-
Review the following program (QueryHistory.java
).
- 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 java.time.Instant;
import java.time.temporal.ChronoUnit;
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.SampleData;
import software.amazon.qldb.tutorial.model.VehicleRegistration;
/**
* Query a table's history for a particular set of documents.
*
* 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 QueryHistory {
public static final Logger log = LoggerFactory.getLogger(QueryHistory.class);
private static final int THREE_MONTHS = 90;
private QueryHistory() { }
/**
* In this example, query the 'VehicleRegistration' history table to find all previous primary owners for a VIN.
*
* @param txn
* The {@link TransactionExecutor} for lambda execute.
* @param vin
* VIN to find previous primary owners for.
* @param query
* The query to find previous primary owners.
* @throws IllegalStateException if failed to convert document ID to an {@link IonValue}.
*/
public static void previousPrimaryOwners(final TransactionExecutor txn, final String vin, final String query) {
try {
final String docId = VehicleRegistration.getDocumentIdByVin(txn, vin);
log.info("Querying the 'VehicleRegistration' table's history using VIN: {}...", vin);
final Result result = txn.execute(query, Constants.MAPPER.writeValueAsIonValue(docId));
ScanTable.printDocuments(result);
} catch (IOException ioe) {
throw new IllegalStateException(ioe);
}
}
public static void main(final String... args) {
final String threeMonthsAgo = Instant.now().minus(THREE_MONTHS, ChronoUnit.DAYS).toString();
final String query = String.format("SELECT data.Owners.PrimaryOwner, metadata.version "
+ "FROM history(VehicleRegistration, `%s`) "
+ "AS h WHERE h.metadata.id = ?", threeMonthsAgo);
ConnectToLedger.getDriver().execute(txn -> {
final String vin = SampleData.VEHICLES.get(0).getVin();
previousPrimaryOwners(txn, vin, query);
});
log.info("Successfully queried history.");
}
}
- 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 com.amazon.ion.IonValue;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import software.amazon.qldb.QldbSession;
import software.amazon.qldb.Result;
import software.amazon.qldb.TransactionExecutor;
import software.amazon.qldb.tutorial.model.SampleData;
import software.amazon.qldb.tutorial.model.VehicleRegistration;
import java.io.IOException;
import java.time.Instant;
import java.time.temporal.ChronoUnit;
import java.util.Collections;
import java.util.List;
/**
* Query a table's history for a particular set of documents.
*
* 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 QueryHistory {
public static final Logger log = LoggerFactory.getLogger(QueryHistory.class);
private static final int THREE_MONTHS = 90;
private QueryHistory() { }
/**
* In this example, query the 'VehicleRegistration' history table to find all previous primary owners for a VIN.
*
* @param txn
* The {@link TransactionExecutor} for lambda execute.
* @param vin
* VIN to find previous primary owners for.
* @param query
* The query to find previous primary owners.
* @throws IllegalStateException if failed to convert document ID to an {@link IonValue}.
*/
public static void previousPrimaryOwners(final TransactionExecutor txn, final String vin, final String query) {
try {
final String docId = VehicleRegistration.getDocumentIdByVin(txn, vin);
final List<IonValue> parameters = Collections.singletonList(Constants.MAPPER.writeValueAsIonValue(docId));
log.info("Querying the 'VehicleRegistration' table's history using VIN: {}...", vin);
final Result result = txn.execute(query, parameters);
ScanTable.printDocuments(result);
} catch (IOException ioe) {
throw new IllegalStateException(ioe);
}
}
public static void main(final String... args) {
final String threeMonthsAgo = Instant.now().minus(THREE_MONTHS, ChronoUnit.DAYS).toString();
final String query = String.format("SELECT data.Owners.PrimaryOwner, metadata.version "
+ "FROM history(VehicleRegistration, `%s`) "
+ "AS h WHERE h.metadata.id = ?", threeMonthsAgo);
ConnectToLedger.getDriver().execute(txn -> {
final String vin = SampleData.VEHICLES.get(0).getVin();
previousPrimaryOwners(txn, vin, query);
}, (retryAttempt) -> log.info("Retrying due to OCC conflict..."));
log.info("Successfully queried history.");
}
}
-
You can view the revision history of a document by querying the built-in History function in the
following syntax.
SELECT * FROM history( table_name
[, `start-time
` [, `end-time
` ] ] ) AS h
[ WHERE h.metadata.id = 'id
' ]
-
The start-time and end-time are both
optional. They're Amazon Ion literal values that can be denoted with backticks
(`...`
). To learn more, see Querying Ion with PartiQL in Amazon QLDB.
-
As a best practice, qualify a history query with both a date range
(start-time and end-time) and a document ID
(metadata.id
). QLDB processes SELECT
queries in transactions,
which are subject to a transaction timeout limit.
QLDB history is indexed by document ID, and you can't create additional history
indexes at this time. History queries that include a start time and end time gain the
benefit of date range qualification.
-
Compile and run the QueryHistory.java
program to query the revision
history of the VehicleRegistration
document with VIN
1N4AL11D75C109151
.
To cryptographically verify a document revision in the vehicle-registration
ledger, proceed to Step 7: Verify a document in a ledger.