使用散列值数组的 AWS DynamoDB Scan 和 FilterExpression

Question

我很难找到在 DynamoDB 上使用 FilterExpression 进行扫描的有用示例 table。我在浏览器中使用 javascript SDK。

我只想扫描我的 table 和 return 那些在我传递给 Scan

的数组中具有 HASH 字段 "UID" 值的记录

假设我有一个唯一 ID 数组，它们是我 table 的哈希字段我想从我的 DynamoDB table 查询这些记录。

类似下面的内容

var idsToSearch=['123','456','789'] //array of the HASH values I would like to retrieve
var tableToSearch = new AWS.DynamoDB();
var scanParams = {
  "TableName":"myAwsTable",  
  "AttributesToGet":['ID','COMMENTS','DATE'],  
  "FilterExpression":"'ID' in "+idsToSearch+"" 

}
tableToSearch.scan(scanParams), function(err,data){
    if (err) console.log(err, err.stack); //error handler
    else console.log(data); //success response
})

Answer 1

您应该使用 IN 运算符。使用 Placeholders for attribute names and attribute values. I would, however, advise against using a Scan in this case. It sounds like you already have the hash key attribute values that you want to find, so it would make more sense to use BatchGetItem.

也更容易

无论如何，这是您在 Java 中的做法：

ScanSpec scanSpec = new ScanSpec()
    .withFilterExpression("#idname in (:val1, :val2, :val3)")
    .withNameMap(ImmutableMap.of("#idname", "ID"))
    .withValueMap(ImmutableMap.of(":val1", "123", ":val2", "456", ":val23", "789"));
ItemCollection<ScanOutcome> = table.scan(scanSpec);

我想象使用 Javascript SDK 会是这样的：

var scanParams = {
  "TableName":"myAwsTable",
  "AttributesToGet": ['ID','COMMENTS','DATE'],
  "FilterExpression": '#idname in (:val1, :val2, :val3)',
  "ExpressionAttributeNames": {
    '#idname': 'ID'
  },
  "ExpressionAttributeValues": {
    ':val1': '123',
    ':val2': '456',
    ':val3': '789'
  }
}

Answer 2

我遇到了这个问题，并通过使用 contains 参数

解决了这个问题

// Object stored in the DB looks like this: 
// [
//     'name' => 'myName',
//     'age' => '24',
//     'gender' => 'Male',
//     'visited' => [
//          'countries': ['Canada', 'USA', 'Japan', 'Australia'],
//          'last_trip': '2015/12/13',
//          'reviews_written': 20
//     ]
// 
// ];

$countries = ['Canada', 'USA', 'Japan', 'Australia'];

$paramToMatch = '24';

$client->query([
        'TableName'     => 'MyDyanmoDB',
        'KeyConditions' => [
            'age' => [
                'AttributeValueList' => [
                    $marshaler->marshalValue($paramToMatch)
                ],
                'ComparisonOperator' => 'EQ'
            ]
        ],
        'ExpressionAttributeNames' => [
            '#visited'   => 'visited',
            '#countries' => 'countries'
        ],
        'ExpressionAttributeValues' => [
            ':countries' => $marshaler->marshalValue($countries)
        ],
        'FilterExpression' => 'contains(:countries, #visited.#countries)',
]);

Answer 3

在下面的示例中，我如何使用“扫描”获取具有特定 ID（“ContentID”）的项目：

var params = {
    TableName: environment.ddbContentTableName,
    ProjectionExpression: "Title, ContentId, Link",
    FilterExpression: "ContentId in (:contentId1, :contentId2, :contentId3, :contentId4)",
    ExpressionAttributeValues: {":contentId1":102,":contentId2":104,":contentId3":103,":contentId4":101}
};

var docClient = new AWS.DynamoDB.DocumentClient();
docClient.scan(params, onQuery);

然后我可以根据已知值以编程方式构建 FilterExpression 和 ExpressionAttributeValues，例如

    // Create the FilterExpression and ExpressionAttributeValues
    var filterExpression =  "ContentId in ("; 

    var expressionAttributeValues = {};

    for (var i = 0; i < currentFavorites.length; i++) { 
        var contentIdName = ":contentId"+(i+1);
        
        if (i==0) {
            filterExpression = filterExpression + contentIdName;
        } else {
            filterExpression = filterExpression + ", " + contentIdName;
        }

        expressionAttributeValues[contentIdName] = currentFavorites[i];
    }

    filterExpression = filterExpression + ")";

    var params = {
        TableName: environment.ddbContentTableName,
        ProjectionExpression: "Title, ContentId, Link",
        FilterExpression: filterExpression,
        ExpressionAttributeValues: expressionAttributeValues
    };

    var docClient = new AWS.DynamoDB.DocumentClient();
    docClient.scan(params, onQuery);

Answer 4

我也在寻找动态解决方案，而不是必须手动将每个参数名称放入条件表达式中。下面是一个解决方案：

List<String> valList= new ArrayList<String>(); // Populate the Values in a List    
StringJoiner valMap =  new StringJoiner(","); // This will be the dynamic Value Map

int i=1;

        table = dynamoDB.getTable(myTable);
        StringBuilder filterExpression = new StringBuilder();
        Map<String, Object> eav = new HashMap<String, Object>();

        if(!valList.isEmpty())
        {
            for(String attrVal: valList)
             {
                eav.put(":val"+i, attrVal);
                valMap.add(":val"+i);
                i++;
            }   
            filterExpression.append("attrColName in ("+valMap.toString()+")"); //here attrColName is the DB attribute
        }

        ItemCollection<ScanOutcome> items;
            items = table.scan(
                filterExpression.toString(), //FilterExpression
                null, //ProjectionExpression - choose all columns
                null, //ExpressionAttributeNames - not used in this example
                eav);//ExpressionAttributeValues

Answer 5

var params = {
TableName: "tableOne",
ProjectionExpression: "Title, ContentId, Link",
FilterExpression: "ContentId in (:contentIds)",
ExpressionAttributeValues: {":contentIds":[11,22,33,44,55]}
};

var docClient = new AWS.DynamoDB.DocumentClient();
docClient.scan(params);

使用散列值数组的 AWS DynamoDB Scan 和 FilterExpression

AWS DynamoDB Scan and FilterExpression using array of hash values

javascript

amazon-web-services

amazon-dynamodb