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, SPECIALIZED_CLASSES

Instance Attribute Summary

Attributes inherited from Innodb::Page

#space

Instance Method Summary collapse

Methods inherited from Innodb::Page

#cursor, #data, #fil_header, #initialize, #inspect, #lsn, maybe_undefined, #next, #offset, parse, #pos_fil_header, #pos_fil_trailer, #prev, #size, #size_fil_header, #size_fil_trailer, #type

Constructor Details

This class inherits a constructor from Innodb::Page

Instance Method Details

#doublewrite_info ⇒ Object

Read the overall doublewrite buffer structures



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# File 'lib/innodb/page/trx_sys.rb', line 69

def doublewrite_info
  c = cursor(pos_doublewrite_info)
  {
    :fseg => Innodb::FsegEntry.get_inode(@space, c),
    :page_info => [
      doublewrite_page_info(c),
      doublewrite_page_info(c),
    ],
    :space_id_stored => c.get_uint32 == DOUBLEWRITE_SPACE_ID_STORED_MAGIC_N,
  }
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 54

def doublewrite_page_info(cursor)
  {
    :magic_n => cursor.get_uint32,
    :page_number => [
      cursor.get_uint32,
      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 94

def dump
  super

  puts "trx_sys:"
  pp trx_sys
  puts
end

#mysql_log_info(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 39

def mysql_log_info(offset)
  c = cursor(offset)
  if c.get_uint32 == MYSQL_LOG_MAGIC_N
    {
      :offset => c.get_uint64,
      :name => c.get_bytes(100),
    }
  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 30

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 24

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 18

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 12

def pos_trx_sys_header
  pos_fil_header + size_fil_header
end

#trx_sys ⇒ Object

Read the TRX_SYS headers and other information.



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# File 'lib/innodb/page/trx_sys.rb', line 82

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