Consultar itens com TTL em uma tabela do DynamoDB usando um SDK da AWS

Os exemplos de código a seguir mostram como consultar itens com TTL.

Java

SDK para Java 2.x

Consulte usando uma expressão filtrada para reunir os itens com TTL em uma tabela do DynamoDB.

import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
import software.amazon.awssdk.services.dynamodb.model.DynamoDbException;
import software.amazon.awssdk.services.dynamodb.model.QueryRequest;
import software.amazon.awssdk.services.dynamodb.model.QueryResponse;
import software.amazon.awssdk.services.dynamodb.model.ResourceNotFoundException;
import software.amazon.awssdk.utils.ImmutableMap;

import java.util.Map;
import java.util.Optional;

        // Get current time in epoch second format (comparing against expiry attribute)
        final long currentTime = System.currentTimeMillis() / 1000;

        // A string that contains conditions that DynamoDB applies after the Query operation, but before the data is returned to you.
        final String keyConditionExpression = "#pk = :pk";

        // The condition that specifies the key values for items to be retrieved by the Query action.
        final String filterExpression = "#ea > :ea";
        final Map<String, String> expressionAttributeNames = ImmutableMap.of(
                "#pk", "primaryKey",
                "#ea", "expireAt");
        final Map<String, AttributeValue> expressionAttributeValues = ImmutableMap.of(
                ":pk", AttributeValue.builder().s(primaryKey).build(),
                ":ea", AttributeValue.builder().s(String.valueOf(currentTime)).build()
        );

        final QueryRequest request = QueryRequest.builder()
                .tableName(tableName)
                .keyConditionExpression(keyConditionExpression)
                .filterExpression(filterExpression)
                .expressionAttributeNames(expressionAttributeNames)
                .expressionAttributeValues(expressionAttributeValues)
                .build();
        try (DynamoDbClient ddb = DynamoDbClient.builder()
                .region(region)
                .build()) {
            final QueryResponse response = ddb.query(request);
            System.out.println(tableName + " Query operation with TTL successful. Request id is "
                    + response.responseMetadata().requestId());
            // Print the items that are not expired
            for (Map<String, AttributeValue> item : response.items()) {
                System.out.println(item.toString());
            }
        } catch (ResourceNotFoundException e) {
            System.err.format("Error: The Amazon DynamoDB table \"%s\" can't be found.\n", tableName);
            System.exit(1);
        } catch (DynamoDbException e) {
            System.err.println(e.getMessage());
            System.exit(1);
        }
        System.exit(0);

• Para obter detalhes da API, consulte Query na Referência da API AWS SDK for Java 2.x.

JavaScript

SDK para JavaScript (v3)

// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
import { DynamoDBClient, QueryCommand } from "@aws-sdk/client-dynamodb";
import { marshall, unmarshall } from "@aws-sdk/util-dynamodb";

async function queryDynamoDBItems(tableName, region, primaryKey) {
    const client = new DynamoDBClient({
        region: region,
        endpoint: `https://dynamodb.${region}.amazonaws.com`
    });

    const currentTime = Math.floor(Date.now() / 1000);

    const params = {
        TableName: tableName,
        KeyConditionExpression: "#pk = :pk",
        FilterExpression: "#ea > :ea",
        ExpressionAttributeNames: {
            "#pk": "primaryKey",
            "#ea": "expireAt"
        },
        ExpressionAttributeValues: marshall({
            ":pk": primaryKey,
            ":ea": currentTime
        })
    };

    try {
        const { Items } = await client.send(new QueryCommand(params));
        Items.forEach(item => {
            console.log(unmarshall(item))
        });
        return Items;
    } catch (err) {
        console.error(`Error querying items: ${err}`);
        throw err;
    }
}

//enter your own values here
queryDynamoDBItems('your-table-name', 'your-partition-key-value');

• Para obter detalhes da API, consulte Query na Referência da API AWS SDK for JavaScript.

Python

SDK para Python (Boto3)

# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: Apache-2.0
import boto3
from datetime import datetime

def query_dynamodb_items(table_name, partition_key):
    """

    :param table_name: Name of the DynamoDB table
    :param partition_key:
    :return:
    """
    try:
        # Initialize a DynamoDB resource
        dynamodb = boto3.resource('dynamodb',
                                  region_name='us-east-1')

        # Specify your table
        table = dynamodb.Table(table_name)

        # Get the current time in epoch format
        current_time = int(datetime.now().timestamp())

        # Perform the query operation with a filter expression to exclude expired items
        # response = table.query(
        #    KeyConditionExpression=boto3.dynamodb.conditions.Key('partitionKey').eq(partition_key),
        #    FilterExpression=boto3.dynamodb.conditions.Attr('expireAt').gt(current_time)
        # )
        response = table.query(
            KeyConditionExpression=dynamodb.conditions.Key('partitionKey').eq(partition_key),
            FilterExpression=dynamodb.conditions.Attr('expireAt').gt(current_time)
        )

        # Print the items that are not expired
        for item in response['Items']:
            print(item)

    except Exception as e:
        print(f"Error querying items: {e}")


# Call the function with your values
query_dynamodb_items('Music', 'your-partition-key-value')

• Para obter detalhes da API, consulte Query na Referência da API AWS SDK para Python (Boto3).

Para ver uma lista completa dos Guias do desenvolvedor de SDK da AWS e exemplos de código, consulte Usar o DynamoDB com um AWS SDK. Este tópico também inclui informações sobre como começar e detalhes sobre versões anteriores do SDK.