DynamoDB Local

Boto3 DynamoDB Docs

Create DynamoDB

• Create local DynamoDB instance for dev environment
• Setting Up DynamoDB Local

java -D"java.library.path=./DynamoDBLocal_lib" -jar DynamoDBLocal.jar -port 7000

Boto3 API

Initiate Resource

• Use 'resource' object whenever possible
• Use 'client' object when necessary. This a lower-level API

import boto3
from boto3.dynamodb.conditions import Key

dynamodb = boto3.resource('dynamodb', endpoint_url='http://localhost:7000')

table = dynamodb.Table('table_name')

• If profile is required:

session = boto3.Session(profile_name='profile')
dynamodb = session.resource('dynamodb')

Read

Query

• Must query by hash key

response = table.query(
    KeyConditionExpression=Key('mall').eq('The Sono Collection')
)

for i in response['Items']:
    print(i)

Scan

• Scans the whole table - inefficient but necessary for non-hash key queries

scan = table.scan()

fe = Key('sort_key').begins_with('TEST#')
response = user_table.scan(
    FilterExpression=fe
)

items = []
for i in response['Items']:
    if i['key'] not in items:
        items.append(i['key'])

Expressions

• FilterExpression

fe = Key('sortkey').begins_with('Test#Hello') & Attr('example').exists()

• ProjectionExpression - Choose which attributes are displayed (Done after the query, different from SELECT)

ProjectionExpression='attribute1, attribute2, attribute3'

Create

Create Table

• Example (Grid Malls)

table = dynamodb.create_table(
    TableName='GridEquip',
    KeySchema=[
        {
            'AttributeName': 'mall',
            'KeyType': 'HASH'
        },
        {
            'AttributeName': 'sortkey',
            'KeyType': 'RANGE'
        }
    ],
    AttributeDefinitions=[
        {
            'AttributeName': 'mall',
            'AttributeType': 'S'
        },
        {
            'AttributeName': 'sortkey',
            'AttributeType': 'S'
        }
    ],
    ProvisionedThroughput={
        'ReadCapacityUnits': 10,
        'WriteCapacityUnits': 10
    }
)

Create Item

response = table.put_item(
    Item={
        stuff
    }
)

Delete

• If using composite key, must supply both hash and range key
• Use ReturnValues param 'ALL_OLD' to have function return deleted item. (Will be in 'Attributes' key of returned object)

response = table.delete_item(
    Key={
        'id': id,
        'sortkey': sortkey
    },
    ReturnValues='ALL_OLD'
)

Update

Update Nested Attribute

{
 'id': 'test'
 'Spam': {
  'Eggs': {'hello: 'hello'}
 }
}

r = table.update_item(Key={'id': 'test'},
 UpdateExpression='SET #spa.#egg = :val',
 ExpressionAttributeNames={
  '#spa': 'Spam',
  '#egg': 'Eggs'
 },
 ExpressionAttributeValues={
  ':val': {'hello': 'goodbye'}
 }
)