使用二级索引从 dynamoDB 获取数据

Question

I am using node js to get data from dynamoDB. However at the moment I am retrieving the data with the UserId. I want to retrieve the data using the secondary index that I have created, which is dateId. My dynamoDB table consists of userId, Exercises, Sets, Reps and dateId. How can I achieve that?

I already tried to add the Index-name under the table name with the dateId value but it's not working.

My dbHelper.js looks like this.

dbHelper.prototype.getExercises = (userID) => {   
return new Promise((resolve, reject) => {     
const params = {     
TableName: tableName,
KeyConditionExpression: "#userID = :user_id", 
ExpressionAttributeNames: {"#userID": "userId"},                
ExpressionAttributeValues: {":user_id": userID }        
}            
docClient.query(params, (err, data) => {                
if (err) {                   
console.error("Unable to read item. Error JSON:", JSON.stringify(err, null, 2));                  
return reject(JSON.stringify(err, null, 2))             
}            
console.log("GetItem succeeded:", JSON.stringify(data, null, 2));                
resolve(data.Items)               
        })
    });
}

My index.js looks like this

const GetExercisesIntentHandler = {      
canHandle(handlerInput) {        
return handlerInput.requestEnvelope.request.type === 'IntentRequest'          
&& handlerInput.requestEnvelope.request.intent.name === 'GetExercisesIntent';      
},      
async handle(handlerInput) {        
const {responseBuilder } = handlerInput;        
const userID = handlerInput.requestEnvelope.context.System.user.userId;         
return dbHelper.getExercises(userID)          
.then((data) => {            
var speechText = 'Your exercises of the day are '             
if (data.length == 0) {              
speechText = "You do not have any favourite exercises yet, add exercise by 
saving add moviename "            
} else {
          speechText += data.map(e => e.Exercise).join(", ")
        }            
return responseBuilder
          .speak(speechText)
          .reprompt(GENERAL_REPROMPT)
          .getResponse();
      })         
.catch((err) => {            
const speechText = "we cannot get your exercise right now. Try again!"            
return responseBuilder
          .speak(speechText)
          .getResponse();          
})      
}   
}

Answer 1

I think your function should look more like this example, based on combining AWS's documentation with your original code.

I think you'll want to supply the partition key for the Index (which I'm assuming is dateId ) rather than the table's partition key.

The ProjectionExpression seems to let us specify a list of attributes to return, and I gather that you want just the Exercises attribute for each item matching the specified dateId .

dbHelper.prototype.getExercises = (dateID) => {   
  return new Promise((resolve, reject) => {
    const
      tableName = NameOfDynamoDbTable, // Must be the actual table name
      indexName = NameOfDynamoDbIndex, // Must be the actual index name on that table
      params = {
        "TableName": tableName,
        "IndexName": indexName,
        "KeyConditionExpression": "#dateID = :date_id",
        "ExpressionAttributeNames": {"#dateID": "dateId"},
        "ExpressionAttributeValues": {":date_id": dateID },
        "ProjectionExpression": "Exercises",
        "ScanIndexForward": true
    };
    docClient.query(params, (err, data) => {
      if (err) {
        console.error("Can't read item. Error JSON:", JSON.stringify(err, null, 2));                  
        return reject(JSON.stringify(err, null, 2));
      }
      console.log("GetItem succeeded:", JSON.stringify(data, null, 2));
      resolve(data.Items)               
    });
  });
};