amazon-web-services - get row by partition key on aws dynamodb

Question

I'm trying to return a a row with id (partition key)

  var db = new AWS.DynamoDB.DocumentClient();
  const id = "123";
  var queryParams = {
    TableName: "students",
    IndexName: "id",
    KeyConditionExpression: "id = :id",
    ExpressionAttributeValues: {
      ":id": id,
    },
  };

  const query = db.query(queryParams).promise();

but is throwing this error:

ValidationException: 1 validation error detected: Value 'id' at 'indexName' failed to satisfy constraint: Member must have length greater than or equal to 3

isn't partition key enough to get a record? I'm confused partition key is not the same as index name?

I also tried with

  var db = new AWS.DynamoDB.DocumentClient();
  var queryParams = {
    TableName: "students",
    Key: {
      id: "123",
    },
  };

  const query = db.get(queryParams).promise();

and it doesn't return anything

标签： amazon-web-servicesamazon-dynamodb

Answer 1

You don't actually have an index named id. You don't need to provide an index when querying on the partition key. Simply remove this line:

IndexName: "id",

Also, note that both table and index names must be 3-255 characters in length (inclusive), which explains the error message that you see.

The following code (both query and get) works fine for me:

const AWS = require('aws-sdk');
AWS.config.update({ region: 'us-east-1' });
const db = new AWS.DynamoDB.DocumentClient();

const ID = "123";
const TABLE_NAME = "students";

const getParams = {
  TableName: TABLE_NAME,
  Key: {
    id: ID,
  },
};

const queryParams = {
  TableName: TABLE_NAME,
  KeyConditionExpression: "id = :id",
  ExpressionAttributeValues: {
    ":id": ID,
  },
};

(async () => {
  const rc1 = await db.get(getParams).promise();
  console.log('get rc:', rc1);

  const rc2 = await db.query(queryParams).promise();
  console.log('query rc:', rc2);
})();