Updating a record

Written by

Yandex Cloud

Updated at November 14, 2024

Unconditional update
Increasing an atomic counter
Conditional update

Read this guide to learn how to make changes to an existing record in the table.

Unconditional update

In the example below, we will update the value of the existing release_date and add the new rating attribute.

To update a movie record in the Series table:

Java

Python

PHP

Node.js

Ruby

Create the SeriesItemOps03 project:
```
mvn -B archetype:generate \
  -DarchetypeGroupId=org.apache.maven.archetypes \
  -DgroupId=com.mycompany.app \
  -DartifactId=SeriesItemOps03
```
As a result of running the command, the system will create the SeriesItemOps03 project folder in the current working folder, with a subfolder structure and the pom.xml project description file.
Go to the project folder:
```
cd SeriesItemOps03
```

Edit the project description in the pom.xml file, for example, using the nano editor:

nano pom.xml

Example of the pom.xml file:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.mycompany.app</groupId>
  <artifactId>SeriesItemOps03</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>SeriesItemOps03</name>
  <url>http://maven.apache.org</url>
  <build>
      <plugins>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-jar-plugin</artifactId>
              <configuration>
                  <archive>
                      <manifest>
                          <addClasspath>true</addClasspath>
                          <classpathPrefix>lib/</classpathPrefix>
                          <mainClass>com.mycompany.app.SeriesItemOps03</mainClass>
                      </manifest>
                      <manifestEntries>
                          <Class-Path>.</Class-Path>
                      </manifestEntries>
                  </archive>
                  <finalName>release/SeriesItemOps03</finalName>
              </configuration>
          </plugin>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-dependency-plugin</artifactId>
              <executions>
                  <execution>
                      <id>copy-dependencies</id>
                      <phase>prepare-package</phase>
                      <goals>
                          <goal>copy-dependencies</goal>
                      </goals>
                      <configuration>
                          <outputDirectory>${project.build.directory}/release/lib</outputDirectory>
                          <overWriteReleases>false</overWriteReleases>
                          <overWriteSnapshots>false</overWriteSnapshots>
                          <overWriteIfNewer>true</overWriteIfNewer>
                      </configuration>
                  </execution>
              </executions>
          </plugin>
      </plugins>
  </build>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>com.amazonaws</groupId>
      <artifactId>aws-java-sdk-dynamodb</artifactId>
      <version>1.11.1012</version>
    </dependency>
  </dependencies>
  <properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>
</project>

Check the current versions of junit and aws-java-sdk-dynamodb.

In the src/main/java/com/mycompany/app/ folder, create the SeriesItemOps03.java file, for example, using the nano editor:

nano src/main/java/com/mycompany/app/SeriesItemOps03.java

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

package com.mycompany.app;

import java.util.Arrays;

import com.amazonaws.client.builder.AwsClientBuilder;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.document.DynamoDB;
import com.amazonaws.services.dynamodbv2.document.Table;
import com.amazonaws.services.dynamodbv2.document.UpdateItemOutcome;
import com.amazonaws.services.dynamodbv2.document.spec.UpdateItemSpec;
import com.amazonaws.services.dynamodbv2.document.utils.ValueMap;
import com.amazonaws.services.dynamodbv2.model.ReturnValue;

public class SeriesItemOps03 {

    public static void main(String[] args) throws Exception {

        AmazonDynamoDB client = AmazonDynamoDBClientBuilder.standard()
            .withEndpointConfiguration(new AwsClientBuilder.EndpointConfiguration("<Document_API_endpoint>", "ru-central1"))
            .build();

        DynamoDB dynamoDB = new DynamoDB(client);

        Table table = dynamoDB.getTable("Series");

        int series_id = 3;
        String title = "Supernatural";

        UpdateItemSpec updateItemSpec = new UpdateItemSpec().withPrimaryKey("series_id", series_id, "title", title)
            .withUpdateExpression("set info.release_date=:d, info.rating=:r")
            .withValueMap(new ValueMap().withString(":d", "2005-09-13").withNumber(":r", 8))
            .withReturnValues(ReturnValue.UPDATED_NEW);

        try {
            System.out.println("Updating record...");
            UpdateItemOutcome outcome = table.updateItem(updateItemSpec);
            System.out.println("Series data updated:\n" + outcome.getItem().toJSONPretty());

        }
        catch (Exception e) {
            System.err.println("Couldn't update record: " + series_id + " " + title);
            System.err.println(e.getMessage());
        }
    }
}

You can add, update, or delete attributes for an existing record using the updateItem method.

This code uses UpdateExpression to describe the updates one needs to perform for the specified record.

The ReturnValues parameter instructs YDB to return only updated attributes (UPDATED_NEW).

Build the project:
```
mvn package
```
This command will create the SeriesItemOps03.jar file in the target/release/ folder.

Run the application:

java -jar target/release/SeriesItemOps03.jar

Result:

Updating record...
Series data updated:
{
  "info" : {
    "release_date" : "2005-09-13",
    "rating" : 8,
    "series_info" : "Supernatural is an American television series created by Eric Kripke"
  }
}

Create the SeriesItemOps03.py file, for example, using the nano editor:

nano SeriesItemOps03.py

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

from decimal import Decimal
from pprint import pprint
import boto3

def update_serie(title, series_id, release_date, rating):
    ydb_docapi_client = boto3.resource('dynamodb', endpoint_url = "<Document_API_endpoint>")

    table = ydb_docapi_client.Table('Series')

    response = table.update_item(
        Key = {
            'series_id': series_id,
            'title': title
        },
        UpdateExpression = "set info.release_date = :d, info.rating = :r ",
        ExpressionAttributeValues = {
            ':d': release_date,
            ':r': Decimal(rating)
        },
        ReturnValues = "UPDATED_NEW"
    )
    return response

if __name__ == '__main__':
    update_response = update_serie(
        "Supernatural", 3, "2005-09-13", 8)
    print("Series data updated:")
    pprint(update_response, sort_dicts = False)

To update a record, use the update_item method. You can use it to update attribute values or add or remove attributes.

The UpdateExpression parameter of the update_item method provides all updates applied to the specified record. The ReturnValues parameter instructs YDB to return only updated attributes (UPDATED_NEW).

In the Boto 3 SDK, the Decimal class is used for storing YDB numeric values.

Run the program:

python SeriesItemOps03.py

Result:

Series data updated:
{'Attributes': {'info': {'release_date': '2005-09-13',
                        'series_info': 'Supernatural is an American '
                                        'television series created by Eric '
                                        'Kripke',
                        'rating': Decimal('8')}},
'ResponseMetadata': {'HTTPStatusCode': 200,
                      'HTTPHeaders': {'content-type': 'application/x-amz-json-1.0',
                                      'x-amz-crc32': '672222905',
                                      'x-request-id': '43c12c64-178b-4144-8766-95dbcf2421b8',
                                      'date': 'Sun, 27 Dec 2020 13:01:12 GMT',
                                      'content-length': '175'},
                      'RetryAttempts': 0}}

Create the SeriesItemOps03.php file, for example, using the nano editor:

nano SeriesItemOps03.php

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

<?php

require 'vendor/autoload.php';

date_default_timezone_set('UTC');

use Aws\DynamoDb\Exception\DynamoDbException;
use Aws\DynamoDb\Marshaler;

$sdk = new Aws\Sdk([
    'endpoint' => '<Document_API_endpoint>',
    'region'   => 'ru-central1',
    'version'  => 'latest'
]);

$dynamodb = $sdk->createDynamoDb();
$marshaler = new Marshaler();

$tableName = 'Series';

$series_id = 3;
$title = 'Supernatural';

$key = $marshaler->marshalJson('
    {
        "series_id": ' . $series_id . ',
        "title": "' . $title . '"
    }
');


$eav = $marshaler->marshalJson('
    {
        ":d": "2005-09-13",
        ":r": 8
    }
');

$params = [
    'TableName' => $tableName,
    'Key' => $key,
    'UpdateExpression' =>
        'set info.release_date=:d, info.rating = :r',
    'ExpressionAttributeValues'=> $eav,
    'ReturnValues' => 'UPDATED_NEW'
];

try {
    $result = $dynamodb->updateItem($params);
    echo "Record updated.\n";
    echo json_encode($result["Attributes"], JSON_PRETTY_PRINT);

} catch (DynamoDbException $e) {
    echo "Couldn't update record:\n";
    echo $e->getMessage() . "\n";
}

?>

This code uses UpdateExpression to describe the updates one needs to perform for the specified record.

The ReturnValues parameter instructs YDB to return only updated attributes (UPDATED_NEW).

Run the program:

php SeriesItemOps03.php

Result:

Record updated.
{
    "info": {
        "M": {
            "rating": {
                "N": "8"
            },
            "release_date": {
                "S": "2005-09-13"
            },
            "series_info": {
                "S": "Supernatural is an American television series created by Eric Kripke"
            }
        }
    }
}

Create the SeriesItemOps03.js file, for example, using the nano editor:

nano SeriesItemOps03.js

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

const AWS = require("@aws-sdk/client-dynamodb");
const { marshall } = require("@aws-sdk/util-dynamodb");

// Credentials should be defined via environment variables AWS_SECRET_ACCESS_KEY and AWS_ACCESS_KEY_ID
const dynamodb = new AWS.DynamoDBClient({
    region: "ru-central1",
    endpoint: "<Document_API_endpoint>",
});

const table = "Series";
const series_id = 3;
const title = "Supernatural";

console.log("Updating record...");

dynamodb.send(new AWS.UpdateItemCommand({
    TableName: table,
    Key: marshall({
        "series_id": series_id,
        "title": title
    }),
    UpdateExpression: "set info.release_date = :d, info.rating = :r",
    ExpressionAttributeValues: marshall({
        ":d": "2005-09-13",
        ":r": 8
    }),
    ReturnValues: "UPDATED_NEW"
}))
    .then(data => {
        console.log("Update successful:", JSON.stringify(data, null, 2));
    })
    .catch(err => {
        console.error("Couldn't update record. JSON error:", JSON.stringify(err, null, 2));
    });

To update the attributes of an existing record, use the UpdateItemCommand command. The UpdateExpression expression describes all the updates you want to perform for the specified element.

The ReturnValues parameter instructs YDB to return only updated attributes (UPDATED_NEW).

Run the program:

node SeriesItemOps03.js

Result:

Updating record...
Update successful: {
  "Attributes": {
    "info": {
      "rating": 8,
      "release_date": "2005-09-13",
      "series_info": "Supernatural is an American television series created by Eric Kripke"
    }
  }
}

Create the SeriesItemOps03.rb file, for example, using the nano editor:

nano SeriesItemOps03.rb

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

require 'aws-sdk-dynamodb'

def table_item_updated?(dynamodb_client, table_item)
  response = dynamodb_client.update_item(table_item)
  puts "Record updated with 'info' attributes:"
  response.attributes['info'].each do |key, value|
    if key == 'rating'
      puts "#{key}: #{value.to_f}"
    else
      puts "#{key}: #{value}"
    end
  end
  true
rescue StandardError => e
  puts "Error updating record: #{e.message}"
  false
end

def run_me
  region = 'ru-central1'
  table_name = 'Series'
  title = 'Supernatural'
  series_id = 3

  Aws.config.update(
    endpoint: '<Document_API_endpoint>',
    region: region
  )

  dynamodb_client = Aws::DynamoDB::Client.new

  table_item = {
    table_name: table_name,
    key: {
      series_id: series_id,
      title: title
    },
    update_expression: 'SET info.release_date = :d, info.rating = :r',
    expression_attribute_values: {
      ':d': '2005-09-13',
      ':r': 8
    },
    return_values: 'UPDATED_NEW'
  }

  puts "Updating the '#{table_name}' table with information about " \
    "'#{title} (#{series_id})'..."

  if table_item_updated?(dynamodb_client, table_item)
    puts 'Table updated.'
  else
    puts 'Couldn't update table.'
  end
end

run_me if $PROGRAM_NAME == __FILE__

This program uses the update_expression expression to describe all the updates that you want to perform for the specified element.

The return_values parameter instructs YDB to return only updated attributes (UPDATED_NEW).

Run the program:

ruby SeriesItemOps03.rb

Result:

Updating the 'Series' table with information about 'Supernatural (3)'...
Record updated with 'info' attributes:
series_info: Supernatural is an American television series created by Eric Kripke
rating: 8.0
release_date: 2005-09-13
Table updated.

Increasing an atomic counter

YDB supports atomic counters.

To increase the rating atomic counter for a series:

Java

Python

PHP

Node.js

Ruby

Create the SeriesItemOps04 project:
```
mvn -B archetype:generate \
  -DarchetypeGroupId=org.apache.maven.archetypes \
  -DgroupId=com.mycompany.app \
  -DartifactId=SeriesItemOps04
```
As a result of running the command, the system will create the SeriesItemOps04 project folder in the current working folder, with a subfolder structure and the pom.xml project description file.
Go to the project folder:
```
cd SeriesItemOps04
```

Edit the project description in the pom.xml file, for example, using nano:

nano pom.xml

Example of the pom.xml file:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.mycompany.app</groupId>
  <artifactId>SeriesItemOps04</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>SeriesItemOps04</name>
  <url>http://maven.apache.org</url>
  <build>
      <plugins>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-jar-plugin</artifactId>
              <configuration>
                  <archive>
                      <manifest>
                          <addClasspath>true</addClasspath>
                          <classpathPrefix>lib/</classpathPrefix>
                          <mainClass>com.mycompany.app.SeriesItemOps04</mainClass>
                      </manifest>
                      <manifestEntries>
                          <Class-Path>.</Class-Path>
                      </manifestEntries>
                  </archive>
                  <finalName>release/SeriesItemOps04</finalName>
              </configuration>
          </plugin>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-dependency-plugin</artifactId>
              <executions>
                  <execution>
                      <id>copy-dependencies</id>
                      <phase>prepare-package</phase>
                      <goals>
                          <goal>copy-dependencies</goal>
                      </goals>
                      <configuration>
                          <outputDirectory>${project.build.directory}/release/lib</outputDirectory>
                          <overWriteReleases>false</overWriteReleases>
                          <overWriteSnapshots>false</overWriteSnapshots>
                          <overWriteIfNewer>true</overWriteIfNewer>
                      </configuration>
                  </execution>
              </executions>
          </plugin>
      </plugins>
  </build>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>com.amazonaws</groupId>
      <artifactId>aws-java-sdk-dynamodb</artifactId>
      <version>1.11.1012</version>
    </dependency>
  </dependencies>
  <properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>
</project>

Check the current versions of junit and aws-java-sdk-dynamodb.

In the src/main/java/com/mycompany/app/ folder, create the SeriesItemOps04.java file, for example, using the nano editor:

nano src/main/java/com/mycompany/app/SeriesItemOps04.java

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

package com.mycompany.app;

import com.amazonaws.client.builder.AwsClientBuilder;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.document.DynamoDB;
import com.amazonaws.services.dynamodbv2.document.Table;
import com.amazonaws.services.dynamodbv2.document.UpdateItemOutcome;
import com.amazonaws.services.dynamodbv2.document.spec.UpdateItemSpec;
import com.amazonaws.services.dynamodbv2.document.utils.ValueMap;
import com.amazonaws.services.dynamodbv2.model.ReturnValue;

public class SeriesItemOps04 {

    public static void main(String[] args) throws Exception {

        AmazonDynamoDB client = AmazonDynamoDBClientBuilder.standard()
            .withEndpointConfiguration(new AwsClientBuilder.EndpointConfiguration("<Document_API_endpoint>", "ru-central1"))
            .build();

        DynamoDB dynamoDB = new DynamoDB(client);

        Table table = dynamoDB.getTable("Series");

        int series_id = 3;
        String title = "Supernatural";

        UpdateItemSpec updateItemSpec = new UpdateItemSpec().withPrimaryKey("series_id", series_id, "title", title)
            .withUpdateExpression("set info.rating = info.rating + :val")
            .withValueMap(new ValueMap().withNumber(":val", 1)).withReturnValues(ReturnValue.UPDATED_NEW);

        try {
            System.out.println("Increasing atomic counter...”);
            UpdateItemOutcome outcome = table.updateItem(updateItemSpec);
            System.out.println("Series data updated:\n" + outcome.getItem().toJSONPretty());

        }
        catch (Exception e) {
            System.err.println("Couldn't update record: " + series_id + " " + title);
            System.err.println(e.getMessage());
        }

    }
}

Use the updateItem method to increase or decrease the value of an existing attribute independently of other write requests (all write requests are applied in the order they are received).

Build the project:
```
mvn package
```
This command will create the SeriesItemOps04.jar file in the target/release/ folder.

Run the application:

java -jar target/release/SeriesItemOps04.jar

Result:

Increasing atomic counter...
Series data updated:
{
  "info" : {
    "release_date" : "2005-09-13",
    "rating" : 9,
    "series_info" : "Supernatural is an American television series created by Eric Kripke"
  }
}

Create the SeriesItemOps04.py file, for example, using the nano editor:

nano SeriesItemOps04.py

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

from decimal import Decimal
from pprint import pprint
import boto3

def increase_rating(title, series_id, rating_increase):
    ydb_docapi_client = boto3.resource('dynamodb', endpoint_url = "<Document_API_endpoint>")

    table = ydb_docapi_client.Table('Series')

    response = table.update_item(
        Key = {
            'series_id': series_id,
            'title': title
        },
        UpdateExpression = "set info.rating = info.rating + :val",
        ExpressionAttributeValues = {
            ':val': Decimal(rating_increase)
        },
        ReturnValues = "UPDATED_NEW"
    )
    return response

if __name__ == '__main__':
    update_response = increase_rating("Supernatural", 3, 1)
    print("Series data updated:")
    pprint(update_response, sort_dicts = False)

Use the update_item method to increase or decrease the value of an existing attribute. In this case, all write requests are applied in the order they arrive.

Each time the program is started, the value of the rating attribute increases by one.

Run the program:

python SeriesItemOps04.py

Result:

Series data updated:
{'Attributes': {'info': {'rating': Decimal('9'),
                        'release_date': '2005-09-13',
                        'series_info': 'Supernatural is an American '
                                        'television series created by Eric '
                                        'Kripke'}},
'ResponseMetadata': {'HTTPStatusCode': 200,
                      'HTTPHeaders': {'content-type': 'application/x-amz-json-1.0',
                                      'x-amz-crc32': '1351796704',
                                      'x-request-id': 'd5fcf336-c3b1-4d07-aaed-bb59f2a609ed',
                                      'date': 'Sun, 27 Dec 2020 13:35:10 GMT',
                                      'content-length': '175'},
                      'RetryAttempts': 0}}

Create the SeriesItemOps04.php file, for example, using the nano editor:

nano SeriesItemOps04.php

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

<?php

require 'vendor/autoload.php';

date_default_timezone_set('UTC');

use Aws\DynamoDb\Exception\DynamoDbException;
use Aws\DynamoDb\Marshaler;

$sdk = new Aws\Sdk([
    'endpoint' => '<Document_API_endpoint>',
    'region'   => 'ru-central1',
    'version'  => 'latest'
]);

$dynamodb = $sdk->createDynamoDb();
$marshaler = new Marshaler();

$tableName = 'Series';

$series_id = 3;
$title = 'Supernatural';

$key = $marshaler->marshalJson('
    {
        "series_id": ' . $series_id . ',
        "title": "' . $title . '"
    }
');

$eav = $marshaler->marshalJson('
    {
        ":val": 1
    }
');

$params = [
    'TableName' => $tableName,
    'Key' => $key,
    'UpdateExpression' => 'set info.rating = info.rating + :val',
    'ExpressionAttributeValues'=> $eav,
    'ReturnValues' => 'UPDATED_NEW'
];

try {
    $result = $dynamodb->updateItem($params);
    echo "Record updated:\n";
    echo json_encode($result["Attributes"], JSON_PRETTY_PRINT);

} catch (DynamoDbException $e) {
    echo "Couldn't update record:\n";
    echo $e->getMessage() . "\n";
}

?>

Each time the above code is run, the rating value increases by one.

Run the program:

php SeriesItemOps04.php

Result:

Record updated:
{
    "info": {
        "M": {
            "rating": {
                "N": "9"
            },
            "release_date": {
                "S": "2005-09-13"
            },
            "series_info": {
                "S": "Supernatural is an American television series created by Eric Kripke"
            }
        }
    }
}

Create the SeriesItemOps04.js file, for example, using the nano editor:

nano SeriesItemOps04.js

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

var AWS = require("aws-sdk");

AWS.config.update({
  region: "ru-central1",
  endpoint: "<Document_API_endpoint>"
});

var docClient = new AWS.DynamoDB.DocumentClient()

var table = "Series";

var series_id = 3;
var title = "Supernatural";

var params = {
    TableName:table,
    Key:{
        "series_id": series_id,
        "title": title
    },
    UpdateExpression: "set info.rating = info.rating + :val",
    ExpressionAttributeValues:{
        ":val": 1
    },
    ReturnValues:"UPDATED_NEW"
};

console.log("Updating record...");
docClient.update(params, function(err, data) {
    if (err) {
        console.error("Couldn't update record. JSON error:", JSON.stringify(err, null, 2));
        process.exit(1);
    } else {
        console.log("Update successful:", JSON.stringify(data, null, 2));
    }
});

Each time the above code is run, the rating value increases by one.

Run the program:

node SeriesItemOps04.js

Result:

Updating record...
Update successful: {
  "Attributes": {
    "info": {
      "rating": 9,
      "release_date": "2005-09-13",
      "series_info": "Supernatural is an American television series created by Eric Kripke"
    }
  }
}

Create the SeriesItemOps04.rb file, for example, using the nano editor:

nano SeriesItemOps04.rb

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

require 'aws-sdk-dynamodb'

def table_item_updated?(dynamodb_client, table_item)
  result = dynamodb_client.update_item(table_item)
  puts "Record updated with 'info' attributes:"
  result.attributes['info'].each do |key, value|
    if key == 'rating'
      puts "#{key}: #{value.to_f}"
    else
      puts "#{key}: #{value}"
    end
  end
  true
rescue StandardError => e
  puts "Error updating record: #{e.message}"
  false
end

def run_me
  region = 'ru-central1'
  table_name = 'Series'
  title = 'Supernatural'
  series_id = 3

  Aws.config.update(
    endpoint: '<Document_API_endpoint>',
    region: region
  )

  dynamodb_client = Aws::DynamoDB::Client.new

  table_item = {
    table_name: table_name,
    key: {
      series_id: series_id,
      title: title
    },
    update_expression: 'SET info.rating = info.rating + :val',
    expression_attribute_values: {
      ':val': 1
    },
    return_values: 'UPDATED_NEW'
  }

  puts "Updating '#{table_name}' with information about " \
    "'#{title} (#{series_id})'..."

  if table_item_updated?(dynamodb_client, table_item)
    puts 'Table updated.'
  else
    puts 'Couldn't update table.'
  end
end

run_me if $PROGRAM_NAME == __FILE__

Each time the above code is run, the rating value increases by one.

Run the program:

ruby SeriesItemOps04.rb

Result:

Updating 'Series' with information about 'Supernatural (3)'...
Record updated with 'info' attributes:
rating: 9.0
release_date: 2005-09-13
series_info: Supernatural is an American television series created by Eric Kripke
Table updated.

Conditional update

To update a record in the Series table when the condition is met:

Java

Python

PHP

Node.js

Ruby

Create the SeriesItemOps05 project:
```
mvn -B archetype:generate \
  -DarchetypeGroupId=org.apache.maven.archetypes \
  -DgroupId=com.mycompany.app \
  -DartifactId=SeriesItemOps05
```
As a result of running the command, the system will create the SeriesItemOps05 project folder in the current working folder, with a subfolder structure and the pom.xml project description file.
Go to the project folder:
```
cd SeriesItemOps05
```

Edit the project description in the pom.xml file, for example, using nano:

nano pom.xml

Example of the pom.xml file:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.mycompany.app</groupId>
  <artifactId>SeriesItemOps05</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>SeriesItemOps05</name>
  <url>http://maven.apache.org</url>
  <build>
      <plugins>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-jar-plugin</artifactId>
              <configuration>
                  <archive>
                      <manifest>
                          <addClasspath>true</addClasspath>
                          <classpathPrefix>lib/</classpathPrefix>
                          <mainClass>com.mycompany.app.SeriesItemOps05</mainClass>
                      </manifest>
                      <manifestEntries>
                          <Class-Path>.</Class-Path>
                      </manifestEntries>
                  </archive>
                  <finalName>release/SeriesItemOps05</finalName>
              </configuration>
          </plugin>
          <plugin>
              <groupId>org.apache.maven.plugins</groupId>
              <artifactId>maven-dependency-plugin</artifactId>
              <executions>
                  <execution>
                      <id>copy-dependencies</id>
                      <phase>prepare-package</phase>
                      <goals>
                          <goal>copy-dependencies</goal>
                      </goals>
                      <configuration>
                          <outputDirectory>${project.build.directory}/release/lib</outputDirectory>
                          <overWriteReleases>false</overWriteReleases>
                          <overWriteSnapshots>false</overWriteSnapshots>
                          <overWriteIfNewer>true</overWriteIfNewer>
                      </configuration>
                  </execution>
              </executions>
          </plugin>
      </plugins>
  </build>
  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.13.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>com.amazonaws</groupId>
      <artifactId>aws-java-sdk-dynamodb</artifactId>
      <version>1.11.1012</version>
    </dependency>
  </dependencies>
  <properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
  </properties>
</project>

Check the current versions of junit and aws-java-sdk-dynamodb.

In the src/main/java/com/mycompany/app/ folder, create the SeriesItemOps05.java file, for example, using the nano editor:

nano src/main/java/com/mycompany/app/SeriesItemOps05.java

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

package com.mycompany.app;

import com.amazonaws.client.builder.AwsClientBuilder;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.document.DynamoDB;
import com.amazonaws.services.dynamodbv2.document.PrimaryKey;
import com.amazonaws.services.dynamodbv2.document.Table;
import com.amazonaws.services.dynamodbv2.document.UpdateItemOutcome;
import com.amazonaws.services.dynamodbv2.document.spec.UpdateItemSpec;
import com.amazonaws.services.dynamodbv2.document.utils.ValueMap;
import com.amazonaws.services.dynamodbv2.model.ReturnValue;

public class SeriesItemOps05 {

    public static void main(String[] args) throws Exception {

        AmazonDynamoDB client = AmazonDynamoDBClientBuilder.standard()
            .withEndpointConfiguration(new AwsClientBuilder.EndpointConfiguration("<Document_API_endpoint>", "ru-central1"))
            .build();

        DynamoDB dynamoDB = new DynamoDB(client);

        Table table = dynamoDB.getTable("Series");

        int series_id = 3;
        String title = "Supernatural";

        UpdateItemSpec updateItemSpec = new UpdateItemSpec()
            .withPrimaryKey(new PrimaryKey("series_id", series_id, "title", title))
            .withUpdateExpression("set info.recommend=:d").withValueMap(new ValueMap().withString(":d", "Recommended for viewing"))
            .withConditionExpression("info.rating > :num").withValueMap(new ValueMap().withString(":d", "Recommended for viewing").withNumber(":num", 9))
            .withReturnValues(ReturnValue.UPDATED_NEW);

        try {
            System.out.println("Attempting to perform conditional update...");
            UpdateItemOutcome outcome = table.updateItem(updateItemSpec);
            System.out.println("Series data updated:\n" + outcome.getItem().toJSONPretty());
        }
        catch (Exception e) {
            System.err.println("Couldn't update record: " + series_id + " " + title);
            System.err.println(e.getMessage());
        }

    }
}

This code shows an example of using the UpdateItem condition. If the condition is true, the update is successful; otherwise, the update is not performed.

In this case, a recommendation about viewing with a rating of more than 9 is added to the record.

Build a project:
```
mvn package
```
This command will create the SeriesItemOps05.jar file in the target/release/ folder.

Run the application:

java -jar target/release/SeriesItemOps05.jar

Result:

Attempting to perform conditional update...
Couldn't update record: 3 Supernatural
Condition not satisfied (Service: AmazonDynamoDBv2; Status Code: 400; Error Code: ConditionalCheckFailedException; Request ID: null; Proxy: null)

Error completing the operation: the movie's rating is 9 and the condition checks the rating higher than 9.

Modify the code so that the condition is 9 or higher:

.withConditionExpression("info.rating >= :num")

Re-build the project and run the application:

mvn package && java -jar target/release/SeriesItemOps05.jar

Now the operation is successful:

Attempting to perform conditional update...
Series data updated:
{
  "info" : {
    "release_date" : "2005-09-13",
    "rating" : 9,
    "recommend" : "Recommended for viewing",
    "series_info" : "Supernatural is an American television series created by Eric Kripke"
  }
}

Create the SeriesItemOps05.py file, for example, using the nano editor:

nano SeriesItemOps05.py

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

from pprint import pprint
import boto3
from botocore.exceptions import ClientError

def add_recommend(title, series_id, rating_val):
    ydb_docapi_client = boto3.resource('dynamodb', endpoint_url = "<Document_API_endpoint>")

    table = ydb_docapi_client.Table('Series')
    rec = "Recommended for viewing"

    try:
        response = table.update_item(
            Key = {
            'series_id': series_id,
            'title': title
        },
            UpdateExpression = "set info.recommend = :d ",
            ConditionExpression = "info.rating > :num",
            ExpressionAttributeValues = {
                ':num': rating_val,
                ':d': rec
        },
            ReturnValues = "UPDATED_NEW"
        )
    except ClientError as e:
        if e.response['Error']['Code'] == "ConditionalCheckFailedException":
            print(e.response['Error']['Message'])
        else:
            raise
    else:
        return response

if __name__ == '__main__':
    print("Attempting conditional update...")
    update_response = add_recommend("Supernatural", 3, 9)
    if update_response:
        print("Series data updated:")
        pprint(update_response, sort_dicts = False)

This code shows an example of using the update_item condition. If the condition is true, the update is successful; otherwise, the update is not performed.

In this case, a recommendation about viewing with a rating of more than 9 is added to the record.

Run the program:
```
python SeriesItemOps05.py
```
Result:
```
Attempting to perform conditional update...
Condition not satisfied
```
The update failed because the series rating is 9 and the condition for update is a rating value higher than 9.
Modify the code so that the condition for the update is a rating of 9 or higher. In this case, the ConditionExpression parameter will look like as follows:
```
ConditionExpression = "info.rating >= :num",
```

Run the program again. The update operation should now be successful.

Result:

Attempting to perform conditional update...
Series data updated:
{'Attributes': {'info': {'release_date': '2005-09-13',
                        'series_info': 'Supernatural is an American '
                                        'television series created by Eric '
                                        'Kripke',
                        'recommend': 'Recommended for viewing',
                        'rating': Decimal('9')}},
'ResponseMetadata': {'HTTPStatusCode': 200,
                      'HTTPHeaders': {'content-type': 'application/x-amz-json-1.0',
                                      'x-amz-crc32': '1812512314',
                                      'x-request-id': 'dcf97598-51f3-419a-b7ba-0b3ad0f5067e',
                                      'date': 'Wed, 13 Jan 2021 10:26:53 GMT',
                                      'content-length': '219'},
                      'RetryAttempts': 0}}

Create the SeriesItemOps05.php file, for example, using the nano editor:

nano SeriesItemOps05.php

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

<?php

require 'vendor/autoload.php';

date_default_timezone_set('UTC');

use Aws\DynamoDb\Exception\DynamoDbException;
use Aws\DynamoDb\Marshaler;

$sdk = new Aws\Sdk([
    'endpoint' => '<Document_API_endpoint>',
    'region'   => 'ru-central1',
    'version'  => 'latest'
]);

$dynamodb = $sdk->createDynamoDb();
$marshaler = new Marshaler();

$tableName = 'Series';

$series_id = 3;
$title = 'Supernatural';

$key = $marshaler->marshalJson('
    {
        "series_id": ' . $series_id . ',
        "title": "' . $title . '"
    }
');

$eav = $marshaler->marshalJson('
    {
      ":d": "Recommended for viewing",
      ":num": 9
    }
');

$params = [
    'TableName' => $tableName,
    'Key' => $key,
    'UpdateExpression' => 'set info.recommend=:d',
    'ConditionExpression' => 'info.rating > :num',
    'ExpressionAttributeValues'=> $eav,
    'ReturnValues' => 'UPDATED_NEW'
];

try {
    $result = $dynamodb->updateItem($params);
    echo "Record updated:\n";
    echo json_encode($result["Attributes"], JSON_PRETTY_PRINT);

} catch (DynamoDbException $e) {
    echo "Couldn't update record:\n";
    echo $e->getMessage() . "\n";
}

?>

This code shows an example of using the UpdateItem condition. If the condition is true, the update is successful; otherwise, the update is not performed.

In this case, a recommendation about viewing with a rating of more than 9 is added to the record.

Run the program:

php SeriesItemOps05.php

Result:

Couldn't update record:
...
ConditionalCheckFailedException (client): Condition not satisfied
...

Error completing the operation: the movie's rating is 9 and the condition checks the rating higher than 9.

Modify the code so that the condition is 9 or higher:

'ConditionExpression' => 'info.rating >= :num',

Run the program again. Now the operation is successful:

Record updated:
{
    "info": {
        "M": {
            "series_info": {
                "S": "Supernatural is an American television series created by Eric Kripke"
            },
            "recommend": {
                "S": "Recommended for viewing"
            },
            "rating": {
                "N": "9"
            },
            "release_date": {
                "S": "2005-09-13"
            }
        }
    }
}

Create the SeriesItemOps05.js file, for example, using the nano editor:

nano SeriesItemOps05.js

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

var AWS = require("aws-sdk");

AWS.config.update({
  region: "ru-central1",
  endpoint: "<Document_API_endpoint>"
});

var docClient = new AWS.DynamoDB.DocumentClient()

var table = "Series";

var series_id = 3;
var title = "Supernatural";

var params = {
    TableName:table,
    Key:{
        "series_id": series_id,
        "title": title
    },
    UpdateExpression: "set info.recommend = :d",
    ConditionExpression: "info.rating > :num",
    ExpressionAttributeValues:{
        ":num": 9,
        ":d": "Recommended for watching"
    },
    ReturnValues:"UPDATED_NEW"
};

console.log("Updating records with specified condition...");
docClient.update(params, function(err, data) {
    if (err) {
        console.error("Couldn't update record. JSON error:", JSON.stringify(err, null, 2));
        process.exit(1);
    } else {
        console.log("Update successful:", JSON.stringify(data, null, 2));
    }
});

This code shows an example of using the UpdateItem condition. If the condition is true, the update is successful; otherwise, the update is not performed.

In this case, a recommendation about viewing with a rating of more than 9 is added to the record.

Run the program:

node SeriesItemOps05.js

Result:

Updating records with specified condition...
Couldn't update record. JSON error: {
  "message": "Condition not satisfied",
  "code": "ConditionalCheckFailedException",
  "time": "2021-06-14T20:12:19.032Z",
  "statusCode": 400,
  "retryable": false,
  "retryDelay": 38.20325040644864
}

Error completing the operation: the movie's rating is 9 and the condition checks the rating higher than 9.

Modify the code so that the condition is 9 or higher:

ConditionExpression: "info.rating >= :num",

Run the program again. Now the operation is successful:

Updating records with specified condition...
Update successful: {
  "Attributes": {
    "info": {
      "rating": 9,
      "release_date": "2005-09-13",
      "series_info": "Supernatural is an American television series created by Eric Kripke",
      "recommend": "Recommended for watching"
    }
  }
}

Create the SeriesItemOps05.rb file, for example, using the nano editor:

nano SeriesItemOps05.rb

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the value you prepared earlier.

require 'aws-sdk-dynamodb'

def table_item_updated?(dynamodb_client, table_item)
  result = dynamodb_client.update_item(table_item)
  puts "Record updated with 'info' attributes:"
  result.attributes['info'].each do |key, value|
    if key == 'rating'
      puts "#{key}: #{value.to_f}"
    else
      puts "#{key}: #{value}"
    end
  end
  true
rescue StandardError => e
  puts "Error updating record: #{e.message}"
  false
end

def run_me
  region = 'ru-central1'
  table_name = 'Series'
  title = 'Supernatural'
  series_id = 3

  Aws.config.update(
    endpoint: '<Document_API_endpoint>',
    region: region
  )

  dynamodb_client = Aws::DynamoDB::Client.new

  table_item = {
    table_name: table_name,
    key: {
      series_id: series_id,
      title: title
    },
    update_expression: 'set info.recommend = :d',
    condition_expression: 'info.rating > :num',
    expression_attribute_values: {
      ':num': 9,
      ':d': 'Recommended for watching'
    },
    return_values: 'UPDATED_NEW'
  }

  puts "Updating the '#{table_name}' table with information about " \
    "'#{title} (#{series_id})'..."

  if table_item_updated?(dynamodb_client, table_item)
    puts 'Table updated.'
  else
    puts 'Couldn't update table.'
  end
end

run_me if $PROGRAM_NAME == __FILE__

This code shows an example of using the update_item condition. If the condition is true, the update is successful; otherwise, the update is not performed.

In this case, a recommendation about viewing with a rating of more than 9 is added to the record.

Run the program:

ruby SeriesItemOps05.rb

Result:

Updating the 'Series' table with information about 'Supernatural (3)'...
Error updating record: Condition not satisfied
Couldn't update table.

Error completing the operation: the movie's rating is 9 and the condition checks the rating higher than 9.

Modify the code so that the condition is 9 or higher:

condition_expression: 'info.rating >= :num',

Run the program again. Now the operation is successful:

Updating the 'Series' table with information about 'Supernatural (3)'...
Record updated with 'info' attributes:
rating: 9.0
release_date: 2005-09-13
series_info: Supernatural is an American television series created by Eric Kripke
recommend: Recommended for watching
Table updated.

Updating a record

Unconditional updateUnconditional update

Increasing an atomic counterIncreasing an atomic counter

Conditional updateConditional update

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Unconditional update

Increasing an atomic counter

Conditional update