Interrogez une table TTL DynamoDB pour obtenir des éléments à l'aide d'un AWS SDK

Les exemples de code suivants montrent comment rechercher des TTL éléments.

Java

SDKpour Java 2.x

Expression filtrée par requête pour rassembler TTL des éléments dans une table 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);

• Pour API plus de détails, voir Requête en AWS SDK for Java 2.x APIréférence.

JavaScript

SDKpour 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');

• Pour API plus de détails, voir Requête en AWS SDK for JavaScript APIréférence.

Python

SDKpour 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')

• Pour API plus de détails, consultez la section Référence Query in AWS SDKfor Python (Boto3). API

Pour obtenir la liste complète des guides AWS SDK de développement et des exemples de code, consultezUtilisation de DynamoDB avec AWS SDK. Cette rubrique inclut également des informations sur la mise en route et des détails sur SDK les versions précédentes.