Class: SDBTools::Selection

Inherits:
Object
  • Object
show all
Includes:
Enumerable
Defined in:
lib/sdbtools/selection.rb

Constant Summary collapse

MAX_BATCH_LIMIT = 
250
DEFAULT_RESULT_LIMIT = 
100

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(sdb, domain, options = {}) ⇒ Selection

Returns a new instance of Selection.



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# File 'lib/sdbtools/selection.rb', line 37

def initialize(sdb, domain, options={})
  @sdb             = sdb
  @domain          = domain.to_s
  @attributes      = options.fetch(:attributes) { :all }
  @conditions      = options[:conditions].to_s
  @order           = options.fetch(:order) { :ascending }
  @order_by        = options.fetch(:order_by) { :none }
  @order_by        = @order_by.to_s unless @order_by == :none
  self.limit       = options.fetch(:limit) { :none }
  self.batch_limit = options.fetch(:batch_limit) { DEFAULT_RESULT_LIMIT }.to_i
  @offset          = options.fetch(:offset) { 0 }.to_i
  @logger          = options.fetch(:logger){::Logger.new($stderr)}
end

Instance Attribute Details

#attributes ⇒ Object

Returns the value of attribute attributes.



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# File 'lib/sdbtools/selection.rb', line 12

def attributes
  @attributes
end

#batch_limit ⇒ Object

Returns the value of attribute batch_limit.



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# File 'lib/sdbtools/selection.rb', line 15

def batch_limit
  @batch_limit
end

#conditions ⇒ Object

Returns the value of attribute conditions.



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# File 'lib/sdbtools/selection.rb', line 13

def conditions
  @conditions
end

#domain ⇒ Object

Returns the value of attribute domain.



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# File 'lib/sdbtools/selection.rb', line 11

def domain
  @domain
end

#limit ⇒ Object

Returns the value of attribute limit.



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# File 'lib/sdbtools/selection.rb', line 14

def limit
  @limit
end

#logger ⇒ Object

Returns the value of attribute logger.



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# File 'lib/sdbtools/selection.rb', line 20

def logger
  @logger
end

#offset ⇒ Object

Returns the value of attribute offset.



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# File 'lib/sdbtools/selection.rb', line 16

def offset
  @offset
end

#order ⇒ Object

Returns the value of attribute order.



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# File 'lib/sdbtools/selection.rb', line 18

def order
  @order
end

#order_by ⇒ Object

Returns the value of attribute order_by.



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# File 'lib/sdbtools/selection.rb', line 17

def order_by
  @order_by
end

#sdb ⇒ Object

Returns the value of attribute sdb.



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# File 'lib/sdbtools/selection.rb', line 19

def sdb
  @sdb
end

#starting_token ⇒ Object 



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# File 'lib/sdbtools/selection.rb', line 118

def starting_token
  @starting_token ||=
    case offset
    when 0 then nil
    else
      op    = offset_count_operation
      count = 0
      op.each do |results, operation|
      count += results[:items].first["Domain"]["Count"].first.to_i
      if count == offset || results[:next_token].nil?
        return results[:next_token]
      end
    end
      raise "Failed to find offset #{offset}"
    end
end

Class Method Details

.quote_name(name) ⇒ Object 



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# File 'lib/sdbtools/selection.rb', line 25

def self.quote_name(name)
  if name.to_s =~ /^[A-Z$_][A-Z0-9$_]*$/i
    name.to_s
  else
    "`" + name.to_s.gsub("`", "``") + "`"
  end
end

.quote_value(value) ⇒ Object 



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# File 'lib/sdbtools/selection.rb', line 33

def self.quote_value(value)
  '"' + value.to_s.gsub(/"/, '""') + '"'
end

Instance Method Details

#count ⇒ Object Also known as: size, length 



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# File 'lib/sdbtools/selection.rb', line 67

def count
  Transaction.open(count_expression) do |t|
    @count ||= count_operation.inject(0){|count, (results, operation)| 
      count += results[:items].first["Domain"]["Count"].first.to_i
    }
  end
end

#count_expression ⇒ Object 



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# File 'lib/sdbtools/selection.rb', line 59

def count_expression
  "SELECT count(*) FROM #{quote_name(domain)}#{match_expression}#{sort_instructions}#{limit_clause_for_count}"
end

#count_operation ⇒ Object 



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# File 'lib/sdbtools/selection.rb', line 106

def count_operation
  Operation.new(sdb, :select, count_expression, :starting_token => starting_token)
end

#each ⇒ Object 



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# File 'lib/sdbtools/selection.rb', line 78

def each
  return if limit == 0
  num_items = 0
  Transaction.open(to_s) do
    select_operation(limit, num_items).each do |results, operation|
      results[:items].each do |item|
        yield(item.keys.first, item.values.first)
        num_items += 1
        return if limit != :none && num_items >= limit
      end
      operation.args[0] = to_s(limit, num_items)
    end
  end
rescue Aws::AwsError => error
  if error.message =~ /InvalidQueryExpression/
    raise error, error.message.to_s + " (#{to_s(limit, num_items)})", error.backtrace
  else
    raise
  end
end

#offset_count_expression ⇒ Object 



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# File 'lib/sdbtools/selection.rb', line 63

def offset_count_expression
  "SELECT count(*) FROM #{quote_name(domain)}#{match_expression}#{sort_instructions} LIMIT #{offset}"
end

#offset_count_operation ⇒ Object 



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# File 'lib/sdbtools/selection.rb', line 110

def offset_count_operation
  Operation.new(sdb, :select, offset_count_expression)
end

#results ⇒ Object 



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# File 'lib/sdbtools/selection.rb', line 99

def results
  @results ||= inject(Arrayfields.new){|results, (name, value)|
    results[name] = value
    results
  }
end

#select_operation(query_limit = limit, offset = 0) ⇒ Object 



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# File 'lib/sdbtools/selection.rb', line 114

def select_operation(query_limit=limit, offset=0)
  Operation.new(sdb, :select, to_s(query_limit, offset), :starting_token => starting_token)
end

#to_s(query_limit = limit, offset = 0) ⇒ Object 



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# File 'lib/sdbtools/selection.rb', line 51

def to_s(query_limit=limit, offset=0)
  "SELECT #{output_list}"       \
  " FROM #{quote_name(domain)}" \
  "#{match_expression}"         \
  "#{sort_instructions}"        \
  "#{limit_clause(query_limit,offset)}"
end