Deleting a record

Written by

Yandex Cloud

Updated at January 30, 2024

To conditionally delete a record from the Series table:

Java

Python

PHP

Node.js

Ruby

Create the SeriesItemOps06 project:
```
mvn -B archetype:generate \
  -DarchetypeGroupId=org.apache.maven.archetypes \
  -DgroupId=com.mycompany.app \
  -DartifactId=SeriesItemOps06
```
As a result of running the command, the SeriesItemOps06 project folder is created in the current working folder with a structure of subfolders and the pom.xml project description file.
Go to the project folder:
```
cd SeriesItemOps06
```

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

nano pom.xml

Sample 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>SeriesItemOps06</artifactId>
  <packaging>jar</packaging>
  <version>1.0-SNAPSHOT</version>
  <name>SeriesItemOps06</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.SeriesItemOps06</mainClass>
                      </manifest>
                      <manifestEntries>
                          <Class-Path>.</Class-Path>
                      </manifestEntries>
                  </archive>
                  <finalName>release/SeriesItemOps06</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 folder src/main/java/com/mycompany/app/, create the SeriesItemOps06.java file, for example, using the nano editor:

nano src/main/java/com/mycompany/app/SeriesItemOps06.java

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the prepared value.

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.spec.DeleteItemSpec;
import com.amazonaws.services.dynamodbv2.document.utils.ValueMap;

public class SeriesItemOps06 {

    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";

        DeleteItemSpec deleteItemSpec = new DeleteItemSpec()
            .withPrimaryKey(new PrimaryKey("series_id", series_id, "title", title)).withConditionExpression("info.rating <= :val")
            .withValueMap(new ValueMap().withNumber(":val", 5));

        try {
            System.out.println("Trying to delete record...");
            table.deleteItem(deleteItemSpec);
            System.out.println("Series data deleted.");
        }
        catch (Exception e) {
            System.err.println("Couldn't delete record: " + series_id + " " + title);
            System.err.println(e.getMessage());
        }

    }
}

This code deletes a movie record if its rating is 5 or lower.

You can use the deleteItem method to delete a single record by specifying its primary key. You can additionally specify ConditionExpression to prevent the element from being deleted if this condition is not satisfied.

Build a project:
```
mvn package
```
As a result of running the command, the SeriesItemOps06.jar file is generated in the folder target/release/.

Run the application:

java -jar target/release/SeriesItemOps06.jar

Result:

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

Error completing operation: film rating is higher than 5.

Change the code by deleting the condition in DeleteItemSpec:

DeleteItemSpec deleteItemSpec = new DeleteItemSpec()
    .withPrimaryKey(new PrimaryKey("series_id", series_id, "title", title));

Re-build the project and run the application:

mvn package && java -jar target/release/SeriesItemOps06.jar

Now the operation is successful:

Attempting to delete record...
Series data deleted.

Create the SeriesItemOps06.py file, for example, using the nano editor:

nano SeriesItemOps06.py

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the prepared value.

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

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

    table = ydb_docapi_client.Table('Series')

    try:
        response = table.delete_item(
            Key = {
                'series_id': series_id,
                'title': title
            },
            ConditionExpression = "info.rating <= :val",
            ExpressionAttributeValues = {
                ":val": Decimal(rating)
            }
        )
    except ClientError as e:
        if e.response['Error']['Code'] == "ConditionalCheckFailedException":
            print(e.response['Error']['Message'])
        else:
            raise
    else:
        return response

if __name__ == '__main__':
    print("Trying to delete record...")
    delete_response = delete_underrated_serie("Supernatural", 3, 5)
    if delete_response:
        print("Series data deleted:")
        pprint(delete_response, sort_dicts = False)

The above code deletes a record if the series rating is 5 or lower.

To delete a record, use the delete_item method, that passes the primary key of the desired item. If necessary, you can set a condition for deleting a record by specifying the ConditionExpression parameter.

Run the program:

python SeriesItemOps06.py

Result:

Attempting to delete record...
Condition not satisfied

Error completing operation: film rating is higher than 5.

Change the code by deleting the condition:

response = table.delete_item(
    Key = {
        'series_id': series_id,
        'title': title
    }
)

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

Result:

Attempting to delete record...
Series data deleted:
{'ResponseMetadata': {'HTTPStatusCode': 200,
                      'HTTPHeaders': {'content-type': 'application/x-amz-json-1.0',
                                      'x-amz-crc32': '2745614147',
                                      'x-request-id': '786fed1d-3c71-4fee-9827-f3f28da0493e',
                                      'date': 'Wed, 13 Jan 2021 11:04:13 GMT',
                                      'content-length': '2'},
                      'RetryAttempts': 0}}

Create the SeriesItemOps06.php file, for example, using the nano editor:

nano SeriesItemOps06.php

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the prepared value.

<?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": 5
    }
');

$params = [
    'TableName' => $tableName,
    'Key' => $key,
    'ConditionExpression' => 'info.rating <= :val',
    'ExpressionAttributeValues'=> $eav
];

try {
    $result = $dynamodb->deleteItem($params);
    echo "Record deleted.\n";

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

?>

This code deletes a movie record if its rating is 5 or lower.

Run the program:

php SeriesItemOps06.php

Result:

Couldn't delete item:
...
ConditionalCheckFailedException (client): Condition not satisfied
...

Error completing operation: film rating is higher than 5.

Change the code by deleting the condition:

$params = [
    'TableName' => $tableName,
    'Key' => $key
];

Run the program again. Now the operation is successful:

Record deleted.

Create the SeriesItemOps06.js file, for example, using the nano editor:

nano SeriesItemOps06.js

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the prepared value.

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";

const params = {
    TableName: table,
    Key: marshall({
        "series_id": series_id,
        "title": title
    }),
    ConditionExpression: "info.rating >= :val",
    ExpressionAttributeValues: marshall({
        ":val": 10
    })
};

console.log("Performing conditional deletion...");

dynamodb.send(new AWS.DeleteItemCommand(params))
    .then(data => {
        console.log("Successfully deleted:", JSON.stringify(data, null, 2));
    })
    .catch(err => {
        console.error("Couldn't delete item. JSON error:", JSON.stringify(err, null, 2));
        process.exit(1);
    })

You can delete a single record by specifying its primary key using the DeleteItemCommand command. If necessary, you can specify the ConditionExpression to prevent the element from being deleted if this condition is not satisfied.

Run the program:

node SeriesItemOps06.js

Result:

Performing conditional deletion...
Couldn't delete record. JSON error: {
  "message": "Condition not satisfied",
  "code": "ConditionalCheckFailedException",
  "time": "2021-06-14T20:33:29.115Z",
  "statusCode": 400,
  "retryable": false,
  "retryDelay": 20.94065998018778
}

Error completing operation: film rating is lower than 10.

Change the code by deleting the condition:

const params = {
    TableName: table,
    Key: marshall({
        "series_id": series_id,
        "title": title
    }),
};

Run the program again. Now the operation is successful:

Performing conditional deletion...
Deletion successful: {}

Create the SeriesItemOps06.rb file, for example, using the nano editor:

nano SeriesItemOps06.rb

Copy the following code to the created file:

Warning

Instead of <Document_API_endpoint>, specify the prepared value.

require 'aws-sdk-dynamodb'

def table_item_deleted?(dynamodb_client, table_item)
  dynamodb_client.delete_item(table_item)
  true
rescue StandardError => e
  puts "Error deleting item: #{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
    },
    condition_expression: 'info.rating > :val',
      expression_attribute_values: {
        ':val' => 9
      }
  }

  puts "Deleting series '#{title} (#{series_id})' from the table '#{table_name}' if the specified condition is satisfied."

  if table_item_deleted?(dynamodb_client, table_item)
    puts 'Record deleted.'
  else
    puts 'Couldn't delete record.'
  end
end

run_me if $PROGRAM_NAME == __FILE__

You can delete a single record by specifying its primary key using the delete method. If necessary, you can specify the ConditionExpression to prevent the element from being deleted if this condition is not satisfied.

Run the program:

ruby SeriesItemOps06.rb

Result:

Deleting series 'Supernatural (3)' from 'Series' table if the specified condition is satisfied.
Error deleting record: condition not satisfied
Couldn't delete record.

Operation failed: film rating is 9.

Change the code by deleting the condition:

table_item = {
  table_name: table_name,
  key: {
    series_id: series_id,
    title: title
  }
}

Run the program again. Now the operation is successful:

Deleting series 'Supernatural (3)' from 'Series' table if the specified condition is satisfied.
Record deleted.

Deleting a record

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