This class is the starting point for working with Amazon SimpleDB.

To use Amazon SimpleDB you must first sign up here.

For more information about Amazon SimpleDB:

• Amazon SimpleDB

• Amazon SimpleDB Documentation

Credentials

You can setup default credentials for all AWS services via AWS.config:

AWS.config(
  :access_key_id => 'YOUR_ACCESS_KEY_ID',
  :secret_access_key => 'YOUR_SECRET_ACCESS_KEY')

Or you can set them directly on the SimpleDB interface:

sdb = AWS::SimpleDB.new(
  :access_key_id => 'YOUR_ACCESS_KEY_ID',
  :secret_access_key => 'YOUR_SECRET_ACCESS_KEY')

Understanding the SimpleDB Interface

SimpleDB stores data in a hierarchy of:

Domains > Items > Attributes

These are modeled with the following classes:

• {DomainCollection}

• {Domain}

• {ItemCollection}

• {Item}

• {AttributeCollection}

• {Attribute}

The collection classes listed above make it easy to enumerate, the objects they represent. They also make it easy to perform bulk operations on all objects in that collection.

Domains

Domains are like database tables. A domain must exist before you can write to it. To create a domain:

sdb = SimpleDB.new
domain = sdb.domains.create('mydomain')

For more information about working with domains see {DomainCollection} and {Domain}.

Items & Attributes

Items exist in SimpleDB when they have attributes. You can delete an item by removing all of its attributes. You create an item by adding an attribute to it.

The following example illustrates how you can reference an item that does not exist yet:

sdb = SimpleDB.new

# this domain is empty, it has no items
domain = sdb.domains.create('newdomain')
domain.items.collect(&:name)
#=> []

# this item doesn't exist yet, so it has no attributes
item = domain.items['newitem']
item.attributes.collect(&:name)
#=> []

# the item has no attributes
tags = item.attributes['tags']
tags.values
#=> []

To create the item in SimpleDB you just need to add an attribute.

tags.add %w(first new)

domain.items.collect(&:name)
#=> ['newitem']

item.attributes.collect(&:name)
#=> ['tags']

tags.values
#=> ['first', 'new']

For more information about working with items and attributes, see:

• {ItemCollection}

• {Item}

• {AttributeCollection}

• {Attribute}

Lazy Execution

Requests are not made until necessary. This means you can drill down all the way to an attribute, by name, without making any requets to SimpleDB.

# makes no request to SimpleDB
sdb = SimpleDB.new
colors = sdb.domains['mydomain'].items['car'].attributes['colors']

# one request to get the values for 'colors'
puts colors.values

# one request to add blue and green
colors.add 'blue', 'green'

# one request to delete the colors attribute
colors.delete