发电机B；获取表中的所有数据-PHP

Question

我在这里找到了一些关于如何通过链接的答案来完成这项工作的帮助。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）。查看文档时，我必须使用LastEvaluatedKey或ExclusiveStartKey来实现分页。任何指导都将不胜感激。

谢谢

Answer 1

我不知道PHP，但这里有一个针对DynamoDB Local运行的Java 8示例，它依赖于编译组：'com.amazonaws'，名称：'aws Java sdk'，版本：'1.10.20'。这显示了Limit（大部分情况下，它不显示过滤器如何影响返回的项目）、LastEvaluatedKey和ExclusiveStarKey的工作方式。您可以看到参数是如何设置的，并将其与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

Answer 2

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，你有用户表，列是用户名和电子邮件

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

foreach($getobj as $cols){

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

}