dynamodb-scan.ts

import * as AWS from 'aws-sdk'

export const fetch = async (startKey?: AWS.DynamoDB.Key | undefined) => {
  const ddb = new AWS.DynamoDB({
    endpoint: 'http://localhost:8000'
  })

  const limit = 6

  const defaultInput: AWS.DynamoDB.ScanInput = {
    TableName: 'ScanSample',
    FilterExpression: '#number = :number',
    ExpressionAttributeNames: {
      '#number': 'number',
    },
    ExpressionAttributeValues: AWS.DynamoDB.Converter.marshall({
      ':number': 2,
    }),
  }

  const responseCount = await ddb.scan({
    ...defaultInput,
    Select: 'COUNT',
  }).promise()

  const result: {
    items: any[];
    key: AWS.DynamoDB.Key | undefined;
  } = {
    items: [],
    key: undefined,
  }

  const fetchItems = async (key: AWS.DynamoDB.Key | undefined) => {
    const response = await ddb.scan({
      ...defaultInput,
      Limit: limit,
      ExclusiveStartKey: key,
    }).promise()

    result.items.push(...(response.Items?.map(item => AWS.DynamoDB.Converter.unmarshall(item)) ?? []))

    if (result.items.length > limit) {
      result.items.splice(limit)

      const keyItem = result.items[result.items.length - 1]

      result.key = {
        id: {
          S: keyItem.id,
        },
        ts: {
          N: String(keyItem.ts),
        },
      }
    } else if (response.LastEvaluatedKey) {
      return fetchItems(response.LastEvaluatedKey)
    }
  }

  await fetchItems(startKey)

  return {
    items: result.items,
    next: result.key ? Buffer.from(JSON.stringify(result.key)).toString('base64') : null,
    count: result.items.length,
    total: responseCount.Count,
  }
}

const key = process.argv[2] ? JSON.parse(Buffer.from(process.argv[2], 'base64').toString()) : undefined

fetch(key).then(data => {
  console.log(JSON.stringify(data))
}).catch(error => {
  console.error(error)
})