使用Boto3的DynamoDB分页

Question

我们正在使用boto3为我们的DynamoDB，我们需要做一个完整的扫描我们的表，以便能够做到这一点，基于其他帖子，我们需要做一个分页。但是，我们无法找到分页的工作示例。这是我们所做的。

import boto3
client_setting = boto3.client('dynamodb', region_name='ap-southeast-2')
paginator = client_setting.get_paginator('scan')
esk = {}
data = []
unconverted_ga = ourQuery(params1, params2)
    for page in unconverted_ga:
        data.append(page)
        esk = page['LastEvaluatedKey']

我们不知道如何将esk作为下一个查询的ExclusiveStartKey。ExclusiveStartkey参数的预期值应该是多少？我们在DynamoDB还是新手，还有很多东西需要学习，包括这个。谢谢

Answer 1

您可以尝试使用以下代码：

esk = None

while True:
    scan_generator = YourTableName.scan(max_results=10, exclusive_start_key=esk)
    for item in scan_generator:
        # your code for processing
    # condition to check if entire table is scanned 
    else:
        break;

    # Load the last keys
    esk = scan_generator.kwargs['exclusive_start_key'].values()

这里是参考文档链接。

希望这能有所帮助

Answer 2

经过一个小时的搜索，我终于找到了一个更好的解决方案。对于那些刚接触DynamoDB的人，我们不应该错过这一点-http://docs.aws.amazon.com/amazondynamodb/latest/gettingstartedguide/GettingStarted.Python.04.html

from __future__ import print_function # Python 2/3 compatibility
import boto3
import json
import decimal
from boto3.dynamodb.conditions import Key, Attr

# Helper class to convert a DynamoDB item to JSON.
class DecimalEncoder(json.JSONEncoder):
    def default(self, o):
        if isinstance(o, decimal.Decimal):
            if o % 1 > 0:
                return float(o)
            else:
                return int(o)
        return super(DecimalEncoder, self).default(o)

dynamodb = boto3.resource('dynamodb', region_name='us-west-2', endpoint_url="http://localhost:8000")

table = dynamodb.Table('Movies')

fe = Key('year').between(1950, 1959)
pe = "#yr, title, info.rating"
# Expression Attribute Names for Projection Expression only.
ean = { "#yr": "year", }
esk = None


response = table.scan(
    FilterExpression=fe,
    ProjectionExpression=pe,
    ExpressionAttributeNames=ean
    )

for i in response['Items']:
    print(json.dumps(i, cls=DecimalEncoder))

// As long as LastEvaluatedKey is in response it means there are still items from the query related to the data
while 'LastEvaluatedKey' in response:
    response = table.scan(
        ProjectionExpression=pe,
        FilterExpression=fe,
        ExpressionAttributeNames= ean,
        ExclusiveStartKey=response['LastEvaluatedKey']
        )

    for i in response['Items']:
        print(json.dumps(i, cls=DecimalEncoder))

Answer 3

根据Tay B在https://stackoverflow.com/a/38619425/3176550

import boto3
dynamodb = boto3.resource('dynamodb',
                          aws_session_token=aws_session_token,
                          aws_access_key_id=aws_access_key_id,
                          aws_secret_access_key=aws_secret_access_key,
                          region_name=region
)

table = dynamodb.Table('widgetsTableName')

response = table.scan()
data = response['Items']

while 'LastEvaluatedKey' in response:
    response = table.scan(ExclusiveStartKey=response['LastEvaluatedKey'])
    data.update(response['Items'])