Class: AWS::SimpleDB

Inherits:
Object
  • Object
show all
Includes:
Core::ServiceInterface
Defined in:
lib/aws/simple_db.rb,
lib/aws/simple_db/item.rb,
lib/aws/simple_db/client.rb,
lib/aws/simple_db/domain.rb,
lib/aws/simple_db/errors.rb,
lib/aws/simple_db/request.rb,
lib/aws/simple_db/attribute.rb,
lib/aws/simple_db/item_data.rb,
lib/aws/simple_db/put_attributes.rb,
lib/aws/simple_db/domain_metadata.rb,
lib/aws/simple_db/item_collection.rb,
lib/aws/simple_db/delete_attributes.rb,
lib/aws/simple_db/domain_collection.rb,
lib/aws/simple_db/attribute_collection.rb,
lib/aws/simple_db/consistent_read_option.rb,
lib/aws/simple_db/expect_condition_option.rb

Overview

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:

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:

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:

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

Defined Under Namespace

Modules: ConsistentReadOption, DeleteAttributes, Errors, ExpectConditionOption, PutAttributes Classes: Attribute, AttributeCollection, Client, Domain, DomainCollection, DomainMetadata, Item, ItemCollection, ItemData, Request

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Core::ServiceInterface

included, #initialize, #inspect

Class Method Details

.consistent_reads(state = true, &block) ⇒ Object

Call this method with a block. Code executed inside the block make consistent reads until the block ends.

AWS::SimpleDB.consistent_reads do
  # ...
end

Other Modes

You can also use this same function to disable consistent reads insie a block. This is useful if you have consistent reads enabled by default:

AWS::SimpleDB.consistent_reads(false) do
  # ...
end

Parameters:

  • state (Boolean) (defaults to: true)

    (true) When true, all SimpleDB read operations will be consistent reads inside the block. When false, all reads operations will not be consistent reads. The previous state will be restored after the block executes.

Returns:

  • Returns the final block value.


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# File 'lib/aws/simple_db.rb', line 192

def self.consistent_reads state = true, &block
  begin
    prev_state = Thread.current['_simple_db_consistent_reads_']
    Thread.current['_simple_db_consistent_reads_'] = state
    yield
  ensure
    Thread.current['_simple_db_consistent_reads_'] = prev_state
  end
end

.consistent_reads_stateBoolean

Returns true if the consistent_reads block has a true state, false otherwise.

Returns:

  • (Boolean)

    Returns true if the consistent_reads block has a true state, false otherwise.


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# File 'lib/aws/simple_db.rb', line 212

def self.consistent_reads_state
  Thread.current['_simple_db_consistent_reads_']
end

.in_consistent_reads_block?Boolean

Returns true if we are inside an AWS::SimpleDB #consistent_reads method block.

Returns:

  • (Boolean)

    Returns true if we are inside an AWS::SimpleDB #consistent_reads method block.


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# File 'lib/aws/simple_db.rb', line 205

def self.in_consistent_reads_block?
  !Thread.current['_simple_db_consistent_reads_'].nil?
end

Instance Method Details

#domainsDomainCollection

Returns a collection object that represents the domains in your account.

Returns:


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# File 'lib/aws/simple_db.rb', line 166

def domains
  DomainCollection.new(:config => config)
end