本文為英文版的機器翻譯版本,如內容有任何歧義或不一致之處,概以英文版為準。
DynamoDB 中的運算存留時間 (TTL)
常見的實作方法是根據項目的建立時間或上次更新時間來TTL設定項目的過期時間。這可以透過將時間新增至 createdAt
和 updatedAt
時間戳記來完成。例如,新建立項目TTL的 可以設定為 createdAt
+ 90 天。當項目更新時, TTL可以重新計算為 updatedAt
+ 90 天。
計算的過期時間必須是 epoch 格式,以秒為單位。若要考慮過期和刪除, 在過去TTL不得超過五年。如果您使用任何其他格式,TTL程序會忽略項目。如果您將過期日期設定為您希望項目過期的未來某個時間,則該項目將在該時間之後過期。例如,假設您將過期日期設定為 1724241326 (即 2024 年 8 月 21 日星期一 11:55:26 (GMT))。項目將在指定的時間之後過期。
建立項目並設定存留時間
下列範例示範如何在建立新項目時使用 expireAt
做為TTL屬性名稱來計算過期時間。指派陳述式會取得目前時間做為變數。在此範例中,過期時間的計算方式為目前時間的 90 天。然後,時間會轉換為 epoch 格式,並在 TTL 屬性中儲存為整數資料類型。
下列程式碼範例示範如何使用 建立項目TTL。
- Java
-
- SDK 適用於 Java 2.x
-
package com.amazon.samplelib.ttl; 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.PutItemRequest; import software.amazon.awssdk.services.dynamodb.model.PutItemResponse; import software.amazon.awssdk.services.dynamodb.model.ResourceNotFoundException; import software.amazon.awssdk.utils.ImmutableMap; import java.io.Serializable; import java.util.Map; import java.util.Optional; public class CreateTTL { public static void main(String[] args) { final String usage = """ Usage: <tableName> <primaryKey> <sortKey> <region> Where: tableName - The Amazon DynamoDB table being queried. primaryKey - The name of the primary key. Also known as the hash or partition key. sortKey - The name of the sort key. Also known as the range attribute. region (optional) - The AWS region that the Amazon DynamoDB table is located in. (Default: us-east-1) """; // Optional "region" parameter - if args list length is NOT 3 or 4, short-circuit exit. if (!(args.length == 3 || args.length == 4)) { System.out.println(usage); System.exit(1); } String tableName = args[0]; String primaryKey = args[1]; String sortKey = args[2]; Region region = Optional.ofNullable(args[3]).isEmpty() ? Region.US_EAST_1 : Region.of(args[3]); // Get current time in epoch second format final long createDate = System.currentTimeMillis() / 1000; // Calculate expiration time 90 days from now in epoch second format final long expireDate = createDate + (90 * 24 * 60 * 60); final ImmutableMap<String, ? extends Serializable> itemMap = ImmutableMap.of("primaryKey", primaryKey, "sortKey", sortKey, "creationDate", createDate, "expireAt", expireDate); final PutItemRequest request = PutItemRequest.builder() .tableName(tableName) .item((Map<String, AttributeValue>) itemMap) .build(); try (DynamoDbClient ddb = DynamoDbClient.builder() .region(region) .build()) { final PutItemResponse response = ddb.putItem(request); System.out.println(tableName + " PutItem operation with TTL successful. Request id is " + response.responseMetadata().requestId()); } 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); } }
-
如需API詳細資訊,請參閱 AWS SDK for Java 2.x API 參考PutItem中的 。
-
- JavaScript
-
- SDK for JavaScript (v3)
-
import { DynamoDBClient, PutItemCommand } from "@aws-sdk/client-dynamodb"; function createDynamoDBItem(table_name, region, partition_key, sort_key) { const client = new DynamoDBClient({ region: region, endpoint: `https://dynamodb.${region}.amazonaws.com` }); // Get the current time in epoch second format const current_time = Math.floor(new Date().getTime() / 1000); // Calculate the expireAt time (90 days from now) in epoch second format const expire_at = Math.floor((new Date().getTime() + 90 * 24 * 60 * 60 * 1000) / 1000); // Create DynamoDB item const item = { 'partitionKey': {'S': partition_key}, 'sortKey': {'S': sort_key}, 'createdAt': {'N': current_time.toString()}, 'expireAt': {'N': expire_at.toString()} }; const putItemCommand = new PutItemCommand({ TableName: table_name, Item: item, ProvisionedThroughput: { ReadCapacityUnits: 1, WriteCapacityUnits: 1, }, }); client.send(putItemCommand, function(err, data) { if (err) { console.log("Exception encountered when creating item %s, here's what happened: ", data, ex); throw err; } else { console.log("Item created successfully: %s.", data); return data; } }); } // use your own values createDynamoDBItem('your-table-name', 'us-east-1', 'your-partition-key-value', 'your-sort-key-value');
-
如需API詳細資訊,請參閱 AWS SDK for JavaScript API 參考PutItem中的 。
-
- Python
-
- SDK for Python (Boto3)
-
import boto3 from datetime import datetime, timedelta def create_dynamodb_item(table_name, region, primary_key, sort_key): """ Creates a DynamoDB item with an attached expiry attribute. :param table_name: Table name for the boto3 resource to target when creating an item :param region: string representing the AWS region. Example: `us-east-1` :param primary_key: one attribute known as the partition key. :param sort_key: Also known as a range attribute. :return: Void (nothing) """ try: dynamodb = boto3.resource('dynamodb', region_name=region) table = dynamodb.Table(table_name) # Get the current time in epoch second format current_time = int(datetime.now().timestamp()) # Calculate the expiration time (90 days from now) in epoch second format expiration_time = int((datetime.now() + timedelta(days=90)).timestamp()) item = { 'primaryKey': primary_key, 'sortKey': sort_key, 'creationDate': current_time, 'expireAt': expiration_time } table.put_item(Item=item) print("Item created successfully.") except Exception as e: print(f"Error creating item: {e}") raise # Use your own values create_dynamodb_item('your-table-name', 'us-west-2', 'your-partition-key-value', 'your-sort-key-value')
-
如需API詳細資訊,請參閱 PutItem 中的 AWS SDK for Python (Boto3) API參考。
-
更新項目並重新整理存留時間
此範例是上一節的接續範例。如果項目已更新,則可以重新計算過期時間。下列範例會將expireAt
時間戳記重新計算為目前時間的 90 天。
下列程式碼範例示範如何更新項目的 TTL。
- Java
-
- SDK 適用於 Java 2.x
-
資料表中現有 DynamoDB 項目TTL的更新。
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.ResourceNotFoundException; import software.amazon.awssdk.services.dynamodb.model.UpdateItemRequest; import software.amazon.awssdk.services.dynamodb.model.UpdateItemResponse; import software.amazon.awssdk.utils.ImmutableMap; import java.util.Map; import java.util.Optional; // Get current time in epoch second format final long currentTime = System.currentTimeMillis() / 1000; // Calculate expiration time 90 days from now in epoch second format final long expireDate = currentTime + (90 * 24 * 60 * 60); // An expression that defines one or more attributes to be updated, the action to be performed on them, and new values for them. final String updateExpression = "SET updatedAt=:c, expireAt=:e"; final ImmutableMap<String, AttributeValue> keyMap = ImmutableMap.of("primaryKey", AttributeValue.fromS(primaryKey), "sortKey", AttributeValue.fromS(sortKey)); final Map<String, AttributeValue> expressionAttributeValues = ImmutableMap.of( ":c", AttributeValue.builder().s(String.valueOf(currentTime)).build(), ":e", AttributeValue.builder().s(String.valueOf(expireDate)).build() ); final UpdateItemRequest request = UpdateItemRequest.builder() .tableName(tableName) .key(keyMap) .updateExpression(updateExpression) .expressionAttributeValues(expressionAttributeValues) .build(); try (DynamoDbClient ddb = DynamoDbClient.builder() .region(region) .build()) { final UpdateItemResponse response = ddb.updateItem(request); System.out.println(tableName + " UpdateItem operation with TTL successful. Request id is " + response.responseMetadata().requestId()); } 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);
-
如需API詳細資訊,請參閱 AWS SDK for Java 2.x API 參考UpdateItem中的 。
-
- JavaScript
-
- SDK for JavaScript (v3)
-
import { DynamoDBClient, UpdateItemCommand } from "@aws-sdk/client-dynamodb"; import { marshall, unmarshall } from "@aws-sdk/util-dynamodb"; async function updateDynamoDBItem(tableName, region, partitionKey, sortKey) { const client = new DynamoDBClient({ region: region, endpoint: `https://dynamodb.${region}.amazonaws.com` }); const currentTime = Math.floor(Date.now() / 1000); const expireAt = Math.floor((Date.now() + 90 * 24 * 60 * 60 * 1000) / 1000); const params = { TableName: tableName, Key: marshall({ partitionKey: partitionKey, sortKey: sortKey }), UpdateExpression: "SET updatedAt = :c, expireAt = :e", ExpressionAttributeValues: marshall({ ":c": currentTime, ":e": expireAt }), }; try { const data = await client.send(new UpdateItemCommand(params)); const responseData = unmarshall(data.Attributes); console.log("Item updated successfully: %s", responseData); return responseData; } catch (err) { console.error("Error updating item:", err); throw err; } } //enter your values here updateDynamoDBItem('your-table-name', 'us-east-1', 'your-partition-key-value', 'your-sort-key-value');
-
如需API詳細資訊,請參閱 AWS SDK for JavaScript API 參考UpdateItem中的 。
-
- Python
-
- SDK for Python (Boto3)
-
import boto3 from datetime import datetime, timedelta def update_dynamodb_item(table_name, region, primary_key, sort_key): """ Update an existing DynamoDB item with a TTL. :param table_name: Name of the DynamoDB table :param region: AWS Region of the table - example `us-east-1` :param primary_key: one attribute known as the partition key. :param sort_key: Also known as a range attribute. :return: Void (nothing) """ try: # Create the DynamoDB resource. dynamodb = boto3.resource('dynamodb', region_name=region) table = dynamodb.Table(table_name) # Get the current time in epoch second format current_time = int(datetime.now().timestamp()) # Calculate the expireAt time (90 days from now) in epoch second format expire_at = int((datetime.now() + timedelta(days=90)).timestamp()) table.update_item( Key={ 'partitionKey': primary_key, 'sortKey': sort_key }, UpdateExpression="set updatedAt=:c, expireAt=:e", ExpressionAttributeValues={ ':c': current_time, ':e': expire_at }, ) print("Item updated successfully.") except Exception as e: print(f"Error updating item: {e}") # Replace with your own values update_dynamodb_item('your-table-name', 'us-west-2', 'your-partition-key-value', 'your-sort-key-value')
-
如需API詳細資訊,請參閱 UpdateItem 中的 AWS SDK for Python (Boto3) API參考。
-
本簡介中討論TTL的範例示範了一種方法,以確保僅將最近更新的項目保留在資料表中。更新的項目會延長其生命週期,而未更新的項目會在建立後過期,並且會免費刪除,從而減少儲存和維護乾淨的資料表。