Class: SimpleDB

Inherits:
Object
  • Object
show all
Includes:
AWS
Defined in:
lib/OriginalAWS/SimpleDB.rb

Constant Summary collapse

ENDPOINT_URI = 
URI.parse("https://sdb.amazonaws.com/")
API_VERSION = 
'2007-11-07'
SIGNATURE_VERSION = 
'1'
HTTP_METHOD =

‘GET’

'POST'

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#prior_box_usage ⇒ Object (readonly)

Returns the value of attribute prior_box_usage.



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# File 'lib/OriginalAWS/SimpleDB.rb', line 21

def prior_box_usage
  @prior_box_usage
end

#total_box_usage ⇒ Object (readonly)

Returns the value of attribute total_box_usage.



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# File 'lib/OriginalAWS/SimpleDB.rb', line 22

def total_box_usage
  @total_box_usage
end

Instance Method Details

#build_attribute_params(attributes = {}, replace = false) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 262

def build_attribute_params(attributes={}, replace=false)
  attribute_params = {}
  index = 0

  attributes.each do |attrib_name, attrib_value|
    attrib_value = [attrib_value] if not attrib_value.is_a? Array

    attrib_value.each do |value|
      attribute_params["Attribute.#{index}.Name"] = attrib_name
      if not value.nil?
        if respond_to? :encode_attribute_value
          # Automatically encode attribute values if the method
          # encode_attribute_value is available in this class
          value = encode_attribute_value(value)
        end
        attribute_params["Attribute.#{index}.Value"] = value
      end
      # Add a Replace parameter for the attribute if the replace flag is set
      attribute_params["Attribute.#{index}.Replace"] = 'true' if replace
      index += 1
    end if attrib_value
  end

  return attribute_params
end

#create_domain(domain_name) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 238

def create_domain(domain_name)
  parameters = build_query_params(API_VERSION, SIGNATURE_VERSION,
    {
    'Action' => 'CreateDomain',
    'DomainName' => domain_name
    })

  do_sdb_query(parameters)
  return true
end

#decode_attribute_value(value_str) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 188

def decode_attribute_value(value_str)
  return '' if value_str.nil?

  # Check whether the '!' flag is present to indicate an encoded value
  return value_str if value_str[0..0] != '!'

  prefix = value_str[0..1].downcase
  if prefix == '!b'
    return decode_boolean(value_str)
  elsif prefix == '!d'
    return decode_date(value_str)
  elsif prefix == '!i'
    return decode_integer(value_str)
  elsif prefix == '!f'
    return decode_float(value_str)
  else
    return value_str
  end
end

#decode_boolean(value_str) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 47

def decode_boolean(value_str)
  if value_str == '!B'
    return false
  elsif value_str == '!b'
    return true
  else
    raise "Cannot decode boolean from string: #{value_str}"
  end
end

#decode_date(value_str) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 63

def decode_date(value_str)
  if value_str[0..1] == '!d'
    return Time.parse(value_str[2..-1])
  else
    raise "Cannot decode date from string: #{value_str}"
  end
end

#decode_float(value_str) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 139

def decode_float(value_str)
  prefix = value_str[0..1]

  if prefix != '!f' and prefix != '!F'
    raise "Cannot decode float from string: #{value_str}"
  end

  value_str =~ /![fF]([0-9]+)!([0-9]+)/
  exp_str = $1
  fraction_str = $2

  max_exp_digits = exp_str.size
  exp_midpoint = (10 ** max_exp_digits) / 2
  max_precision_digits = fraction_str.size

  if prefix == '!F'
    sign = -1
    exp = exp_midpoint - exp_str.to_i

    fraction_upper_bound = (10 ** max_precision_digits)
    fraction = fraction_upper_bound - BigDecimal(fraction_str)
  else
    sign = 1
    exp = exp_str.to_i - exp_midpoint

    fraction = BigDecimal(fraction_str)
  end

  return sign * "0.#{fraction.to_i}".to_f * (10 ** exp)
end

#decode_integer(value_str) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 88

def decode_integer(value_str)
  if value_str[0..1] == '!I'
    # Encoded value is a negative integer
    max_digits = value_str.size - 2
    upper_bound = (10 ** max_digits)

    return value_str[2..-1].to_i - upper_bound
  elsif value_str[0..1] == '!i'
    # Encoded value is a positive integer
    return value_str[2..-1].to_i
  else
    raise "Cannot decode integer from string: #{value_str}"
  end
end

#delete_attributes(domain_name, item_name, attributes = {}) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 304

def delete_attributes(domain_name, item_name, attributes={})
  parameters = build_query_params(API_VERSION, SIGNATURE_VERSION,
    {
    'Action' => 'DeleteAttributes',
    'DomainName' => domain_name,
    'ItemName' => item_name
    })

  parameters.merge!(build_attribute_params(attributes))

  do_sdb_query(parameters)
  return true
end

#delete_domain(domain_name) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 250

def delete_domain(domain_name)
  parameters = build_query_params(API_VERSION, SIGNATURE_VERSION,
    {
    'Action' => 'DeleteDomain',
    'DomainName' => domain_name
    })

  do_sdb_query(parameters)
  return true
end

#do_sdb_query(parameters) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 25

def do_sdb_query(parameters)
  response = do_query(HTTP_METHOD, ENDPOINT_URI, parameters)
  xml_doc = REXML::Document.new(response.body)

  @total_box_usage = 0 if @total_box_usage.nil?

  @prior_box_usage = xml_doc.elements['//BoxUsage'].text.to_f
  @total_box_usage += @prior_box_usage

  return xml_doc
end

#encode_attribute_value(value) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 171

def encode_attribute_value(value)
  if value == true or value == false
    return encode_boolean(value)
  elsif value.is_a? Time
    return encode_date(value)
  elsif value.is_a? Integer
    return encode_integer(value)
  elsif value.is_a? Numeric
    return encode_float(value)
  else
    # No type-specific encoding is available, so we simply convert
    # the value to a string.
    return value.to_s
  end
end

#encode_boolean(value) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 38

def encode_boolean(value)
  if value
    return '!b'
  else
    return '!B'
  end
end

#encode_date(value) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 58

def encode_date(value)
  return "!d" + value.getutc.iso8601
end

#encode_float(value, max_exp_digits = 2, max_precision_digits = 15) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 104

def encode_float(value, max_exp_digits=2, max_precision_digits=15)
  exp_midpoint = (10 ** max_exp_digits) / 2

  sign, fraction, base, exponent = BigDecimal(value.to_s).split

  if exponent >= exp_midpoint or exponent < -exp_midpoint
    raise "Exponent #{exponent} is outside encoding range " +
      "(-#{exp_midpoint} " + "to #{exp_midpoint - 1})"
  end

  if fraction.size > max_precision_digits
    # Round fraction value if it exceeds allowed precision.
    fraction_str = fraction[0...max_precision_digits] + '.' +
                   fraction[max_precision_digits..-1]
    fraction = BigDecimal(fraction_str).round(0).split[1]
  elsif fraction.size < max_precision_digits
    # Right-pad fraction with zeros if it is too short.
    fraction = fraction + ('0' * (max_precision_digits - fraction.size))
  end

  # The zero value is a special case, for which the exponent must be 0
  exponent = -exp_midpoint if value == 0

  if sign == 1
    return format("!f%0#{max_exp_digits}d", exp_midpoint + exponent) +
      format("!%0#{max_precision_digits}d", fraction.to_i)
  else
    fraction_upper_bound = (10 ** max_precision_digits)
    diff_fraction = fraction_upper_bound - BigDecimal(fraction)
    return format("!F%0#{max_exp_digits}d", exp_midpoint - exponent) +
      format("!%0#{max_precision_digits}d", diff_fraction)
  end
end

#encode_integer(value, max_digits = 18) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 72

def encode_integer(value, max_digits=18)
  upper_bound = (10 ** max_digits)

  if value >= upper_bound or value < -upper_bound
    raise "Integer #{value} is outside encoding range (-#{upper_bound} " +
      "to #{upper_bound - 1})"
  end

  if value < 0
    return "!I" + format("%0#{max_digits}d", upper_bound + value)
  else
    return "!i" + format("%0#{max_digits}d", value)
  end
end

#get_attributes(domain_name, item_name, attribute_name = nil) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 319

def get_attributes(domain_name, item_name, attribute_name=nil)
  parameters = build_query_params(API_VERSION, SIGNATURE_VERSION,
    {
    'Action' => 'GetAttributes',
    'DomainName' => domain_name,
    'ItemName' => item_name,
    'AttributeName' => attribute_name
    })

  xml_doc = do_sdb_query(parameters)

  attributes = {}
  xml_doc.elements.each('//Attribute') do |attribute_node|
    attr_name = attribute_node.elements['Name'].text
    value = attribute_node.elements['Value'].text

    if respond_to? :decode_attribute_value
      # Automatically decode attribute values if the method
      # decode_attribute_value is available in this class
      value = decode_attribute_value(value)
    end

    # An empty attribute value is an empty string, not nil.
    value = '' if value.nil?

    if attributes.has_key?(attr_name)
      attributes[attr_name] << value
    else
      attributes[attr_name] = [value]
    end
  end

  if not attribute_name.nil?
    # If a specific attribute was requested, return only the values array
    # for this attribute.
    if not attributes[attribute_name]
      return []
    else
      return attributes[attribute_name]
    end
  else
    return attributes
  end
end

#list_domains(max_domains = 100) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 209

def list_domains(max_domains=100)
  more_domains = true
  next_token = nil
  domain_names = []

  while more_domains
    parameters = build_query_params(API_VERSION, SIGNATURE_VERSION,
      {
      'Action' => 'ListDomains',
      'MaxNumberOfDomains' => max_domains,
      'NextToken' => next_token
      })

    xml_doc = do_sdb_query(parameters)

    xml_doc.elements.each('//DomainName') do |name|
      domain_names << name.text
    end

    # If we receive a NextToken element, perform a follow-up operation
    # to retrieve the next set of domain names.
    next_token = xml_doc.elements['//NextToken/text()']
    more_domains = !next_token.nil?
  end

  return domain_names
end

#put_attributes(domain_name, item_name, attributes, replace = false) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 289

def put_attributes(domain_name, item_name, attributes, replace=false)
  parameters = build_query_params(API_VERSION, SIGNATURE_VERSION,
    {
    'Action' => 'PutAttributes',
    'DomainName' => domain_name,
    'ItemName' => item_name
    })

  parameters.merge!(build_attribute_params(attributes, replace))

  do_sdb_query(parameters)
  return true
end

#query(domain_name, query_expression = nil, options = {:fetch_all=>true}) ⇒ Object 



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# File 'lib/OriginalAWS/SimpleDB.rb', line 365

def query(domain_name, query_expression=nil, options={:fetch_all=>true})
  more_items = true
  next_token = nil
  item_names = []

  while more_items
    parameters = build_query_params(API_VERSION, SIGNATURE_VERSION,
      {
      'Action' => 'Query',
      'DomainName' => domain_name,
      'QueryExpression' => query_expression,
      'MaxNumberOfItems' => options[:max_items],
      'NextToken' => next_token
      })

    xml_doc = do_sdb_query(parameters)

    xml_doc.elements.each('//ItemName') do |item_name|
      item_names << item_name.text
    end

    if xml_doc.elements['//NextToken']
      next_token = xml_doc.elements['//NextToken'].text.gsub("\n","")
      more_items = options[:fetch_all]
    else
      more_items = false
    end
  end

  return item_names
end

#query_with_attributes(domain_name, query_expression = nil, attribute_names = [], options = {:fetch_all=>true}) ⇒ Object

The query with attributes feature was added to the S3 API after the release of “Programming Amazon Web Services” so it is not discussed in the book’s text. For more details, see: www.jamesmurty.com/2008/09/07/samples-for-simpledb-querywithattributes/



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# File 'lib/OriginalAWS/SimpleDB.rb', line 401

def query_with_attributes(domain_name, query_expression=nil, 
                          attribute_names=[], options={:fetch_all=>true})
  more_items = true
  next_token = nil
  items = []

  while more_items
    parameters = build_query_params(API_VERSION, SIGNATURE_VERSION,
      {
      'Action' => 'QueryWithAttributes',
      'DomainName' => domain_name,
      'QueryExpression' => query_expression,
      'MaxNumberOfItems' => options[:max_items],
      'NextToken' => next_token
      },{
      'AttributeName' => attribute_names,
      })

    xml_doc = do_sdb_query(parameters)

    xml_doc.elements.each('//Item') do |item_node|
      item = {'name' => item_node.elements['Name'].text}
          
      attributes = {}
      item_node.elements.each('Attribute') do |attribute_node|
        attr_name = attribute_node.elements['Name'].text
        value = attribute_node.elements['Value'].text

        if respond_to? :decode_attribute_value
          # Automatically decode attribute values if the method
          # decode_attribute_value is available in this class
          value = decode_attribute_value(value)
        end

        # An empty attribute value is an empty string, not nil.
        value = '' if value.nil?

        if attributes.has_key?(attr_name)
          attributes[attr_name] << value
        else
          attributes[attr_name] = [value]
        end
      end
  
      item['attributes'] = attributes
      items << item
    end

    if xml_doc.elements['//NextToken']
      next_token = xml_doc.elements['//NextToken'].text.gsub("\n","")
      more_items = options[:fetch_all]
    else
      more_items = false
    end
  end

  return items
end