使用哈希值数组的AWS DynamoDB Scan和FilterExpression [英] AWS DynamoDB Scan and FilterExpression using array of hash values

问题描述

我很难找到一个在DynamoDB表上使用FilterExpression进行扫描的有用示例。我在浏览器中使用javascript SDK。

I am having a hard time finding a useful example for a scan with FilterExpression on a DynamoDB table. I am using the javascript SDK in the browser.

我想扫描我的表并仅返回那些在传递给Scan的数组中具有HASH字段UID值的记录

I would like to scan my table and return only those records that have HASH field "UID" values within an array I pass to the Scan

假设我有一组唯一的id是我表的哈希字段
我想从DynamoDB表中查询这些记录。

Lets say I have an array of unique ids that are the hash field of my table I would like to query these records from my DynamoDB table.

如下所示

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
})

推荐答案

你应该使用 IN 运算符。对于属性名称和属性值，使用占位符也更容易。 但是，我建议不要在这种情况下使用扫描 。听起来您已经拥有了要查找的哈希键属性值，因此使用 BatchGetItem 。

You should make use of the IN operator. It is also easier to use 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.

无论如何，这是你要怎么做它在Java中：

Anyways, here is how you would do it in Java:

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);

我想用Javascript SDK会是这样的：

I would imagine using the Javascript SDK it would be something like this:

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

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