Class: Innodb::Page::TrxSys

Inherits:
Innodb::Page show all
Defined in:
lib/innodb/page/trx_sys.rb

Overview

A specialized class for TRX_SYS pages, which contain various information about the transaction system within InnoDB. Only one TRX_SYS page exists in any given InnoDB installation, and it is page 5 of the system tablespace (space 0), most commonly named “ibdata1”.

The basic structure of a TRX_SYS page is: FIL header, TRX_SYS header, empty space, master binary log information, empty space, local binary log information, empty space, doublewrite information (repeated twice), empty space, and FIL trailer.

Constant Summary collapse

MYSQL_LOG_MAGIC_N =

A magic number present in each MySQL binary log information structure, which helps identify whether the structure is populated or not.

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DOUBLEWRITE_MAGIC_N =

A magic number present in each doublewrite buffer information structure, which helps identify whether the structure is populated or not.

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DOUBLEWRITE_SPACE_ID_STORED_MAGIC_N =

A magic number present in the overall doublewrite buffer structure, which identifies whether the space id is stored.

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Constants inherited from Innodb::Page

PAGE_TYPE, PAGE_TYPE_BY_VALUE, SPECIALIZED_CLASSES

Instance Attribute Summary

Attributes inherited from Innodb::Page

#space

Instance Method Summary collapse

Methods inherited from Innodb::Page

#calculate_checksum, #checksum, #corrupt?, #cursor, #data, #fil_header, handle, #initialize, #inspect, #lsn, maybe_undefined, #next, #offset, parse, #pos_fil_header, #pos_fil_trailer, #pos_page_body, #prev, #size, #size_fil_header, #size_fil_trailer, #type

Constructor Details

This class inherits a constructor from Innodb::Page

Instance Method Details

#binary_log ⇒ Object 



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# File 'lib/innodb/page/trx_sys.rb', line 132

def binary_log;   trx_sys[:binary_log];   end

#doublewrite ⇒ Object 



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# File 'lib/innodb/page/trx_sys.rb', line 134

def doublewrite;  trx_sys[:doublewrite];  end

#doublewrite_info(cursor) ⇒ Object

Read the overall doublewrite buffer structures



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# File 'lib/innodb/page/trx_sys.rb', line 90

def doublewrite_info(cursor)
  cursor.peek(pos_doublewrite_info) do |c_doublewrite|
    c_doublewrite.name("doublewrite") do |c|
      {
        :fseg => c.name("fseg") { Innodb::FsegEntry.get_inode(@space, c) },
        :page_info => [
          c.name("group[0]") { doublewrite_page_info(c) },
          c.name("group[1]") { doublewrite_page_info(c) },
        ],
        :space_id_stored =>
          (c.name("space_id_stored") { c.get_uint32 } ==
             DOUBLEWRITE_SPACE_ID_STORED_MAGIC_N),
      }
    end
  end
end

#doublewrite_page_info(cursor) ⇒ Object

Read a single doublewrite buffer information structure from a given cursor.



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# File 'lib/innodb/page/trx_sys.rb', line 75

def doublewrite_page_info(cursor)
  {
    :magic_n => cursor.name("magic_n") { cursor.get_uint32 },
    :page_number => [
      cursor.name("page[0]") { cursor.get_uint32 },
      cursor.name("page[1]") { cursor.get_uint32 },
    ],
  }
end

#dump ⇒ Object

Dump the contents of a page for debugging purposes.



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# File 'lib/innodb/page/trx_sys.rb', line 137

def dump
  super

  puts "trx_sys:"
  pp trx_sys
  puts
end

#fseg ⇒ Object 



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# File 'lib/innodb/page/trx_sys.rb', line 130

def fseg;         trx_sys[:fseg];         end

#master_log ⇒ Object 



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# File 'lib/innodb/page/trx_sys.rb', line 133

def master_log;   trx_sys[:master_log];   end

#mysql_log_info(cursor, offset) ⇒ Object

Read a MySQL binary log information structure from a given position.



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# File 'lib/innodb/page/trx_sys.rb', line 59

def mysql_log_info(cursor, offset)
  cursor.peek(offset) do |c|
    if c.name("magic_n") { c.get_uint32 } == MYSQL_LOG_MAGIC_N
      {
        :offset => c.name("offset") { c.get_uint64 },
        :name   => c.name("name")   { c.get_bytes(100) },
      }
    end
  end
end

#pos_doublewrite_info ⇒ Object

The doublewrite buffer information is located 200 bytes from the end of the page.



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# File 'lib/innodb/page/trx_sys.rb', line 31

def pos_doublewrite_info
  size - 200
end

#pos_mysql_binary_log_info ⇒ Object

The local binary log information is located 1000 bytes from the end of the page.



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# File 'lib/innodb/page/trx_sys.rb', line 25

def pos_mysql_binary_log_info
  size - 1000
end

#pos_mysql_master_log_info ⇒ Object

The master’s binary log information is located 2000 bytes from the end of the page.



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# File 'lib/innodb/page/trx_sys.rb', line 19

def pos_mysql_master_log_info
  size - 2000
end

#pos_trx_sys_header ⇒ Object

The TRX_SYS header immediately follows the FIL header.



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# File 'lib/innodb/page/trx_sys.rb', line 13

def pos_trx_sys_header
  pos_fil_header + size_fil_header
end

#rsegs ⇒ Object 



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# File 'lib/innodb/page/trx_sys.rb', line 131

def rsegs;        trx_sys[:rsegs];        end

#rsegs_array(cursor) ⇒ Object 



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# File 'lib/innodb/page/trx_sys.rb', line 39

def rsegs_array(cursor)
  @rsegs_array ||= (0...256).to_a.inject([]) do |a, n|
    cursor.name("slot[#{n}]") do |c|
      slot = {
        :space_id => c.name("space_id") {
          Innodb::Page.maybe_undefined(c.get_uint32)
        },
        :page_number => c.name("page_number") {
          Innodb::Page.maybe_undefined(c.get_uint32)
        },
      }
      if slot[:space_id] && slot[:page_number]
        a << slot
      end
    end
    a
  end
end

#trx_id ⇒ Object 



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# File 'lib/innodb/page/trx_sys.rb', line 129

def trx_id;       trx_sys[:trx_id];       end

#trx_sys ⇒ Object

Read the TRX_SYS headers and other information.



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# File 'lib/innodb/page/trx_sys.rb', line 108

def trx_sys
  @trx_sys ||= cursor(pos_trx_sys_header).name("trx_sys") do |c|
    {
      :trx_id       => c.name("trx_id") { c.get_uint64 },
      :fseg         => c.name("fseg") {
        Innodb::FsegEntry.get_inode(@space, c)
      },
      :rsegs        => c.name("rsegs") {
        rsegs_array(c)
      },
      :binary_log   => c.name("binary_log") {
        mysql_log_info(c, pos_mysql_binary_log_info)
      },
      :master_log   => c.name("master_log") {
        mysql_log_info(c, pos_mysql_master_log_info)
      },
      :doublewrite  => doublewrite_info(c),
    }
  end
end