Terjemahan disediakan oleh mesin penerjemah. Jika konten terjemahan yang diberikan bertentangan dengan versi bahasa Inggris aslinya, utamakan versi bahasa Inggris.
Bekerja dengan item kedaluwarsa dan waktu untuk hidup () TTL
Item kedaluwarsa yang tertunda penghapusan dapat difilter dari operasi baca dan tulis. Ini berguna dalam skenario ketika data kedaluwarsa tidak lagi valid dan tidak boleh digunakan. Jika tidak difilter, mereka akan terus ditampilkan dalam operasi baca dan tulis sampai dihapus oleh proses latar belakang.
Barang-barang ini masih diperhitungkan untuk penyimpanan dan biaya baca sampai dihapus.
TTLpenghapusan dapat diidentifikasi di DynamoDB Streams, tetapi hanya di Wilayah tempat penghapusan terjadi. TTLpenghapusan yang direplikasi ke wilayah tabel global tidak dapat diidentifikasi dalam aliran DynamoDB di wilayah tempat penghapusan direplikasi.
Filter item kedaluwarsa dari operasi baca
Untuk operasi baca seperti Pindai dan Kueri, ekspresi filter dapat memfilter item kedaluwarsa yang menunggu penghapusan. Seperti yang ditunjukkan pada cuplikan kode berikut, ekspresi filter dapat menyaring item yang TTL waktunya sama dengan atau kurang dari waktu saat ini. Misalnya, SDK kode Python menyertakan pernyataan penugasan yang memperoleh waktu saat ini sebagai variabel (now
), dan mengubahnya menjadi int
format waktu epoch.
Contoh kode berikut menunjukkan bagaimana untuk query untuk TTL item.
- Java
-
- SDKuntuk Java 2.x
-
Query Filtered Expression untuk mengumpulkan TTL item dalam tabel 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);
- JavaScript
-
- SDKuntuk JavaScript (v3)
-
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');
- Python
-
- SDKuntuk Python (Boto3)
-
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')
Menulis secara kondisional ke item yang kedaluwarsa
Ekspresi kondisi dapat digunakan untuk menghindari penulisan terhadap item yang kedaluwarsa. Cuplikan kode di bawah ini adalah pembaruan bersyarat yang memeriksa apakah waktu kedaluwarsa lebih besar dari waktu saat ini. Jika benar, operasi tulis akan berlanjut.
Contoh kode berikut menunjukkan cara memperbarui item secara kondisional. TTL
- Java
-
- SDKuntuk 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.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;
public class UpdateTTLConditional {
public static void main(String[] args) {
final String usage = """
Usage:
<tableName> <primaryKey> <sortKey> <newTtlAttribute> <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.
newTtlAttribute - New attribute name (as part of the update command)
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 == 4 || args.length == 5)) {
System.out.println(usage);
System.exit(1);
}
final String tableName = args[0];
final String primaryKey = args[1];
final String sortKey = args[2];
final String newTtlAttribute = args[3];
Region region = Optional.ofNullable(args[4]).isEmpty() ? Region.US_EAST_1 : Region.of(args[4]);
// 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 newTtlAttribute = :val1";
// A condition that must be satisfied in order for a conditional update to succeed.
final String conditionExpression = "expireAt > :val2";
final ImmutableMap<String, AttributeValue> keyMap =
ImmutableMap.of("primaryKey", AttributeValue.fromS(primaryKey),
"sortKey", AttributeValue.fromS(sortKey));
final Map<String, AttributeValue> expressionAttributeValues = ImmutableMap.of(
":val1", AttributeValue.builder().s(newTtlAttribute).build(),
":val2", AttributeValue.builder().s(String.valueOf(expireDate)).build()
);
final UpdateItemRequest request = UpdateItemRequest.builder()
.tableName(tableName)
.key(keyMap)
.updateExpression(updateExpression)
.conditionExpression(conditionExpression)
.expressionAttributeValues(expressionAttributeValues)
.build();
try (DynamoDbClient ddb = DynamoDbClient.builder()
.region(region)
.build()) {
final UpdateItemResponse response = ddb.updateItem(request);
System.out.println(tableName + " UpdateItem operation with conditional 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);
}
}
- JavaScript
-
- SDKuntuk JavaScript (v3)
-
Perbarui TTL pada Item DynamoDB yang ada dalam tabel, dengan kondisi.
import { DynamoDBClient, UpdateItemCommand } from "@aws-sdk/client-dynamodb";
import { marshall, unmarshall } from "@aws-sdk/util-dynamodb";
const updateDynamoDBItem = async (tableName, region, partitionKey, sortKey, newAttribute) => {
const client = new DynamoDBClient({
region: region,
endpoint: `https://dynamodb.${region}.amazonaws.com`
});
const currentTime = Math.floor(Date.now() / 1000);
const params = {
TableName: tableName,
Key: marshall({
artist: partitionKey,
album: sortKey
}),
UpdateExpression: "SET newAttribute = :newAttribute",
ConditionExpression: "expireAt > :expiration",
ExpressionAttributeValues: marshall({
':newAttribute': newAttribute,
':expiration': currentTime
}),
ReturnValues: "ALL_NEW"
};
try {
const response = await client.send(new UpdateItemCommand(params));
const responseData = unmarshall(response.Attributes);
console.log("Item updated successfully: ", responseData);
return responseData;
} catch (error) {
if (error.name === "ConditionalCheckFailedException") {
console.log("Condition check failed: Item's 'expireAt' is expired.");
} else {
console.error("Error updating item: ", error);
}
throw error;
}
};
// Enter your values here
updateDynamoDBItem('your-table-name', "us-east-1",'your-partition-key-value', 'your-sort-key-value', 'your-new-attribute-value');
- Python
-
- SDKuntuk Python (Boto3)
-
import boto3
from datetime import datetime, timedelta
from botocore.exceptions import ClientError
def update_dynamodb_item(table_name, region, primary_key, sort_key, ttl_attribute):
"""
Updates an existing record in a DynamoDB table with a new or updated TTL attribute.
: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.
:param ttl_attribute: name of the TTL attribute in the target DynamoDB table
:return:
"""
try:
dynamodb = boto3.resource('dynamodb', region_name=region)
table = dynamodb.Table(table_name)
# Generate updated TTL in epoch second format
updated_expiration_time = int((datetime.now() + timedelta(days=90)).timestamp())
# Define the update expression for adding/updating a new attribute
update_expression = "SET newAttribute = :val1"
# Define the condition expression for checking if 'expireAt' is not expired
condition_expression = "expireAt > :val2"
# Define the expression attribute values
expression_attribute_values = {
':val1': ttl_attribute,
':val2': updated_expiration_time
}
response = table.update_item(
Key={
'primaryKey': primary_key,
'sortKey': sort_key
},
UpdateExpression=update_expression,
ConditionExpression=condition_expression,
ExpressionAttributeValues=expression_attribute_values
)
print("Item updated successfully.")
return response['ResponseMetadata']['HTTPStatusCode'] # Ideally a 200 OK
except ClientError as e:
if e.response['Error']['Code'] == "ConditionalCheckFailedException":
print("Condition check failed: Item's 'expireAt' is expired.")
else:
print(f"Error updating item: {e}")
except Exception as e:
print(f"Error updating item: {e}")
# replace with your values
update_dynamodb_item('your-table-name', 'us-east-1', 'your-partition-key-value', 'your-sort-key-value',
'your-ttl-attribute-value')
Mengidentifikasi item yang dihapus di DynamoDB Streams
Catatan stream berisi bidang identitas pengguna Records[<index>].userIdentity
. Item yang dihapus oleh TTL proses memiliki bidang berikut:
Records[<index>].userIdentity.type
"Service"
Records[<index>].userIdentity.principalId
"dynamodb.amazonaws.com"
Berikut ini JSON menunjukkan bagian yang relevan dari catatan aliran tunggal:
"Records": [
{
...
"userIdentity": {
"type": "Service",
"principalId": "dynamodb.amazonaws.com"
}
...
}
]