动态数据库；获取表中的所有数据 - PHP

Question

我通过here 链接的答案找到了一些帮助。 但它不适合我的用例。 我的目标是获取 DynamoDB 表中的所有记录（用户名和电子邮件）。浏览文档我必须使用 LastEvaluatedKey 或 ExclusiveStartKey 来实现分页。任何指导将不胜感激。

谢谢

Answer 1

此查询将能够从 DynamoDB 表中获取所有记录。

function scanAllData($table,$limit){

  $result = $this->getClientdb()->scan(array(
        'TableName' => $table,
        'Limit' => $limit,
        'Select' => 'ALL_ATTRIBUTES'                
     ),
    array('limit' => $limit),
  );
    return $result['Items'];
}

你可以这样调用这个函数。例如，您有“用户”表，列是 usernames 和 emails

$getobj = $this->scanAllData('users','10');

foreach($getobj as $cols){

   echo $cols['usernames']['S'];
   echo $cols['emails']['S'];    

}

Answer 2

我不了解 PHP，但这里有一个针对 DynamoDB Local 运行的 Java 8 示例，它依赖于 compile group: 'com.amazonaws', name: 'aws-java-sdk', version: '1.10.20'。这显示了Limit（大多数情况下，它不显示过滤器如何影响返回的项目）、LastEvaluatedKey 和ExclusiveStartKey 是如何工作的。你可以看到参数是如何设置的，并与 PHP 示例进行比较：

import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClient;
import com.amazonaws.services.dynamodbv2.document.DynamoDB;
import com.amazonaws.services.dynamodbv2.document.Item;
import com.amazonaws.services.dynamodbv2.document.Table;
import com.amazonaws.services.dynamodbv2.model.AttributeDefinition;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
import com.amazonaws.services.dynamodbv2.model.CreateTableRequest;
import com.amazonaws.services.dynamodbv2.model.KeySchemaElement;
import com.amazonaws.services.dynamodbv2.model.KeyType;
import com.amazonaws.services.dynamodbv2.model.ProvisionedThroughput;
import com.amazonaws.services.dynamodbv2.model.ScalarAttributeType;
import com.amazonaws.services.dynamodbv2.model.ScanRequest;
import com.amazonaws.services.dynamodbv2.model.ScanResult;
import com.amazonaws.services.dynamodbv2.util.Tables;
import com.google.common.collect.ImmutableList;

import java.util.Map;

public class ScanExample {

    private static final String TABLE_NAME = "test_table";
    private static final String HASH_ATTR_NAME = "hash";

    public static void main(String[] args) throws InterruptedException {
        AWSCredentials awsCredentials = new BasicAWSCredentials("key", "secret");
        AmazonDynamoDB dynamoDBClient = new AmazonDynamoDBClient(awsCredentials);
        dynamoDBClient.setEndpoint("http://localhost:4000");

        if (Tables.doesTableExist(dynamoDBClient, TABLE_NAME)) {
            dynamoDBClient.deleteTable(TABLE_NAME);
        }

        CreateTableRequest createTableRequest = new CreateTableRequest();
        createTableRequest.setTableName(TABLE_NAME);
        createTableRequest.setProvisionedThroughput(new ProvisionedThroughput(50l, 50l));

        createTableRequest.withKeySchema(
                ImmutableList.of(new KeySchemaElement(HASH_ATTR_NAME, KeyType.HASH)))
                .withAttributeDefinitions(ImmutableList.of(
                                new AttributeDefinition(HASH_ATTR_NAME, ScalarAttributeType.N))
                );

        dynamoDBClient.createTable(createTableRequest);
        Tables.awaitTableToBecomeActive(dynamoDBClient, TABLE_NAME);

        final Table table = new DynamoDB(dynamoDBClient).getTable(TABLE_NAME);
        createItems(table, 8);

        final int limit = 3;
        performScan(dynamoDBClient, limit);
    }

    private static void performScan(final AmazonDynamoDB client, final int limit) {
        ScanRequest scanRequest = new ScanRequest(TABLE_NAME)
                .withLimit(limit);

        Map<String, AttributeValue> exclusiveStartKey = null;
        do {
            final ScanResult scanResult = client.scan(scanRequest);
            System.out.println("With exclusiveStartKey=" + exclusiveStartKey);
            scanResult.getItems().forEach(System.out::println);
            exclusiveStartKey = scanResult.getLastEvaluatedKey();
            System.out.println("Result lastEvaluatedKey=" + exclusiveStartKey);
            // Reusing same request object, just setting the start key
            scanRequest.setExclusiveStartKey(exclusiveStartKey);
            System.out.println();
        } while(exclusiveStartKey != null);
    }

    private static void createItems(final Table table, final int n) {
        for (int i = 0; i < n; i++) {
            table.putItem(new Item().withNumber(HASH_ATTR_NAME, i));
        }
    }
}

示例输出：

With exclusiveStartKey=null
{hash={N: 2,}}
{hash={N: 1,}}
{hash={N: 3,}}
Result lastEvaluatedKey={hash={N: 3,}}

With exclusiveStartKey={hash={N: 3,}}
{hash={N: 5,}}
{hash={N: 7,}}
{hash={N: 0,}}
Result lastEvaluatedKey={hash={N: 0,}}

With exclusiveStartKey={hash={N: 0,}}
{hash={N: 6,}}
{hash={N: 4,}}
Result lastEvaluatedKey=null