Class: Innodb::UndoRecord

Inherits:
Object
  • Object
show all
Defined in:
lib/innodb/undo_record.rb

Overview

A single undo log record.

Constant Summary collapse

TYPE =

Possible undo record types.

{
  11 => :insert,
  12 => :update_existing,
  13 => :update_deleted,
  14 => :delete,
}
TYPE_MASK = 
0x0f
COMPILATION_INFO_MASK = 
0x70
COMPILATION_INFO_SHIFT = 
4
COMPILATION_INFO_NO_ORDER_CHANGE_BV = 
1
COMPILATION_INFO_NO_SIZE_CHANGE_BV = 
2
EXTERN_FLAG = 
0x80

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(undo_page, position) ⇒ UndoRecord

Returns a new instance of UndoRecord.



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# File 'lib/innodb/undo_record.rb', line 11

def initialize(undo_page, position)
  @undo_page = undo_page
  @position = position

  @undo_log = nil
  @index_page = nil
end

Instance Attribute Details

#index_page ⇒ Object

Returns the value of attribute index_page.



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# File 'lib/innodb/undo_record.rb', line 9

def index_page
  @index_page
end

#position ⇒ Object (readonly)

Returns the value of attribute position.



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# File 'lib/innodb/undo_record.rb', line 6

def position
  @position
end

#undo_log ⇒ Object

Returns the value of attribute undo_log.



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# File 'lib/innodb/undo_record.rb', line 8

def undo_log
  @undo_log
end

#undo_page ⇒ Object (readonly)

Returns the value of attribute undo_page.



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# File 'lib/innodb/undo_record.rb', line 5

def undo_page
  @undo_page
end

Instance Method Details

#cursor(position) ⇒ Object

Return a BufferCursor starting before the header.



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# File 'lib/innodb/undo_record.rb', line 43

def cursor(position)
  new_cursor = @undo_page.cursor(position)
  if @undo_log
    new_cursor.push_name("undo_log[#{@undo_log.position}]")
  end
  new_cursor.push_name("undo_record[#{@position}]")
  new_cursor
end

#dump ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 267

def dump
  puts "Undo record at offset %i" % offset
  puts

  puts "Header:"
  puts "  %-25s: %i" % ["Previous record offset", header[:prev]]
  puts "  %-25s: %i" % ["Next record offset", header[:next]]
  puts "  %-25s: %s" % ["Type", header[:type]]
  puts

  puts "System fields:"
  puts "  Transaction ID: %s" % trx_id
  puts "  Roll Pointer:"
  puts "    Undo Log: page %i, offset %i" % [
    roll_ptr[:undo_log][:page],
    roll_ptr[:undo_log][:offset],
  ]
  puts "    Rollback Segment ID: %i" % roll_ptr[:rseg_id]
  puts

  puts "Key fields:"
  key.each do |field|
    puts "  %s: %s" % [
      field[:name],
      field[:value].inspect,
    ]
  end
  puts

  puts "Non-key fields:"
  row.each do |field|
    next if !field
    puts "  %s: %s" % [
      field[:name],
      field[:value].inspect,
    ]
  end
  puts
end

#get(prev_or_next) ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 95

def get(prev_or_next)
  if header[prev_or_next] != 0
    new_undo_record = new_subordinate(@undo_page, header[prev_or_next])
    if new_undo_record.type
      new_undo_record
    end
  end
end

#has_previous_version? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/innodb/undo_record.rb', line 91

def has_previous_version?
  [:update_existing, :update_deleted, :delete].include?(type)
end

#header ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 67

def header
  @header ||= cursor(pos_header).name("header") do |c|
    header = {
      :prev => c.name("prev") { c.get_uint16 },
      :next => c.name("next") { c.get_uint16 },
    }

    info = c.name("info") { c.get_uint8 }
    cmpl = (info & COMPILATION_INFO_MASK) >> COMPILATION_INFO_SHIFT
    header[:type] = TYPE[info & TYPE_MASK]
    header[:extern_flag] = (info & EXTERN_FLAG) != 0
    header[:info] = {
      :order_may_change => (cmpl & COMPILATION_INFO_NO_ORDER_CHANGE_BV) == 0,
      :size_may_change  => (cmpl & COMPILATION_INFO_NO_SIZE_CHANGE_BV) == 0,
    }

    header
  end
end

#key ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 204

def key
  undo_record[:key]
end

#key_string ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 216

def key_string
  key && key.map { |r| "%s=%s" % [r[:name], r[:value].inspect] }.join(", ")
end

#new_subordinate(undo_page, position) ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 19

def new_subordinate(undo_page, position)
  new_undo_record = self.class.new(undo_page, position)
  new_undo_record.undo_log = undo_log
  new_undo_record.index_page = index_page

  new_undo_record
end

#next ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 108

def next
  get(:next)
end

#offset ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 212

def offset
  undo_record[:offset]
end

#page ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 208

def page
  undo_record[:page]
end

#pos_header ⇒ Object

The header really starts 2 bytes before the undo record position, as the pointer to the previous record is written there.



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# File 'lib/innodb/undo_record.rb', line 29

def pos_header
  @position - 2
end

#pos_record ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 38

def pos_record
  pos_header + size_header
end

#prev ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 104

def prev
  get(:prev)
end

#prev_by_history ⇒ Object

Find the previous row version by following the roll_ptr from one undo record to the next (backwards through the record version history). Since we are operating without the benefit of knowing about active transactions and without protection from purge, check that everything looks sane before returning it.



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# File 'lib/innodb/undo_record.rb', line 237

def prev_by_history
  unless has_previous_version?
    # This undo record type has no previous version information.
    return nil
  end

  undo_log = roll_ptr[:undo_log]
  older_undo_page = @undo_page.space.page(undo_log[:page])

  unless older_undo_page and older_undo_page.is_a?(Innodb::Page::UndoLog)
    # The page was probably re-used for something else.
    return nil
  end

  older_undo_record = new_subordinate(older_undo_page,
                                      undo_log[:offset])

  unless older_undo_record and table_id == older_undo_record.table_id
    # The record space was probably re-used for something else.
    return nil
  end

  unless older_undo_record.trx_id.nil? or trx_id >= older_undo_record.trx_id
    # The trx_id should not be newer; but may be absent (for insert).
    return nil
  end

  older_undo_record
end

#read_record ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 116

def read_record
  cursor(pos_record).name("record") do |c|
    this_record = {
      :page => undo_page.offset,
      :offset => position,
      :header => header,
      :undo_no => c.name("undo_no") { c.get_imc_uint64 },
      :table_id => c.name("table_id") { c.get_imc_uint64 },
    }

    if has_previous_version?
      this_record[:info_bits] = c.name("info_bits") { c.get_uint8 }
      this_record[:trx_id] = c.name("trx_id") { c.get_ic_uint64 }
      this_record[:roll_ptr] = c.name("roll_ptr") {
        Innodb::DataType::RollPointerType.parse_roll_pointer(c.get_ic_uint64)
      }
    end

    if index_page
      read_record_fields(this_record, c)
    else
      # Slurp up the remaining data as a string.
      this_record[:data] = c.get_bytes(header[:next] - c.position - 2)
    end

    this_record
  end
end

#read_record_fields(this_record, c) ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 145

def read_record_fields(this_record, c)
  this_record[:key] = []
  index_page.record_format[:key].each do |field|
    this_record[:key][field.position] = {
      :name => field.name,
      :type => field.data_type.name,
      :value => c.name(field.name) {
        field_length = c.name("field_length") { c.get_ic_uint32 }
        field.value_by_length(c, field_length)
      }
    }
  end

  if has_previous_version?
    field_count = c.name("field_count") { c.get_ic_uint32 }
    this_record[:row] = Array.new(index_page.record_format[:row].size)
    field_count.times do
      field_number = c.name("field_number[#{field_count}]") { c.get_ic_uint32 }
      field = nil
      field_index = nil
      index_page.record_format[:row].each_with_index do |candidate_field, index|
        if candidate_field.position == field_number
          field = candidate_field
          field_index = index
        end
      end
      raise "Unknown field #{field_number}" unless field
      this_record[:row][field_index] = {
        :name => field.name,
        :type => field.data_type.name,
        :value => c.name(field.name) {
          field_length = c.name("field_length") { c.get_ic_uint32 }
          field.value_by_length(c, field_length)
        }
      }
    end
  end
end

#record_size ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 112

def record_size
  header[:next] - @position - size_header
end

#roll_ptr ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 200

def roll_ptr
  undo_record[:roll_ptr]
end

#row ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 220

def row
  undo_record[:row]
end

#row_string ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 224

def row_string
  row && row.select { |r| !r.nil? }.map { |r| r && "%s=%s" % [r[:name], r[:value].inspect] }.join(", ")
end

#size_header ⇒ Object

The size of the header.



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# File 'lib/innodb/undo_record.rb', line 34

def size_header
  2 + 2 + 1
end

#string ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 228

def string
  "(%s) → (%s)" % [key_string, row_string]
end

#table_id ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 192

def table_id
  undo_record[:table_id]
end

#trx_id ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 196

def trx_id
  undo_record[:trx_id]
end

#type ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 87

def type
  header[:type]
end

#undo_no ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 188

def undo_no
  undo_record[:undo_no]
end

#undo_record ⇒ Object 



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# File 'lib/innodb/undo_record.rb', line 184

def undo_record
  @undo_record ||= read_record
end