Interroga una tabella DynamoDB per gli elementi TTL utilizzando un SDK AWS

I seguenti esempi di codice mostrano come eseguire una query per gli elementi TTL.

Java

SDK per Java 2.x

Interroga l'espressione filtrata per raccogliere elementi TTL in una tabella 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);

• Per ulteriori informazioni sulle API, consulta Query nella Documentazione di riferimento delle API AWS SDK for Java 2.x .

JavaScript

SDK per (v3) JavaScript

// 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');

• Per ulteriori informazioni sulle API, consulta Query nella Documentazione di riferimento delle API AWS SDK for JavaScript .

Python

SDK per 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')

• Per informazioni dettagliate sulle API, consulta Query nella Documentazione di riferimento per l’API SDK for Python (Boto3)AWS .

Per un elenco completo delle guide per sviluppatori AWS SDK e degli esempi di codice, consulta. Utilizzo di DynamoDB con un SDK AWS Questo argomento include anche informazioni su come iniziare e dettagli sulle versioni precedenti dell'SDK.