Class: Innodb::Page::Index

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

Overview

A specialized class for handling INDEX pages, which contain a portion of the data from exactly one B+tree. These are typically the most common type of page in any database.

The basic structure of an INDEX page is: FIL header, INDEX header, FSEG header, fixed-width system records (infimum and supremum), user records (the actual data) which grow ascending by offset, free space, the page directory which grows descending by offset, and the FIL trailer.

Direct Known Subclasses

Compressed

Defined Under Namespace

Classes: Compressed, RecordCursor

Constant Summary collapse

RECORD_NEXT_SIZE =

The size (in bytes) of the "next" pointer in each record header.

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RECORD_REDUNDANT_BITS_SIZE =

The size (in bytes) of the bit-packed fields in each record header for "redundant" record format.

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RECORD_REDUNDANT_OFF1_OFFSET_MASK =

Masks for 1-byte record end-offsets within "redundant" records.

0x7f
RECORD_REDUNDANT_OFF1_NULL_MASK = 
0x80
RECORD_REDUNDANT_OFF2_OFFSET_MASK =

Masks for 2-byte record end-offsets within "redundant" records.

0x3fff
RECORD_REDUNDANT_OFF2_NULL_MASK = 
0x8000
RECORD_REDUNDANT_OFF2_EXTERN_MASK = 
0x4000
RECORD_COMPACT_BITS_SIZE =

The size (in bytes) of the bit-packed fields in each record header for "compact" record format.

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PAGE_DIRECTION =

Page direction values possible in the page_header's :direction field.

{
  1 => :left,           # Inserts have been in descending order.
  2 => :right,          # Inserts have been in ascending order.
  3 => :same_rec,       # Unused by InnoDB.
  4 => :same_page,      # Unused by InnoDB.
  5 => :no_direction,   # Inserts have been in random order.
}
RECORD_TYPES =

Record types used in the :type field of the record header.

{
  0 => :conventional,   # A normal user record in a leaf page.
  1 => :node_pointer,   # A node pointer in a non-leaf page.
  2 => :infimum,        # The system "infimum" record.
  3 => :supremum,       # The system "supremum" record.
}
RECORD_INFO_MIN_REC_FLAG =

This record is the minimum record at this level of the B-tree.

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RECORD_INFO_DELETED_FLAG =

This record has been marked as deleted.

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PAGE_DIR_SLOT_SIZE =

The size (in bytes) of the record pointers in each page directory slot.

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PAGE_DIR_SLOT_MIN_N_OWNED =

The minimum number of records "owned" by each record with an entry in the page directory.

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PAGE_DIR_SLOT_MAX_N_OWNED =

The maximum number of records "owned" by each record with an entry in the page directory.

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Constants inherited from Innodb::Page

PAGE_TYPE, PAGE_TYPE_BY_VALUE, SPECIALIZED_CLASSES

Instance Attribute Summary collapse

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 Attribute Details

#record_describer ⇒ Object

Returns the value of attribute record_describer.



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# File 'lib/innodb/page/index.rb', line 14

def record_describer
  @record_describer
end

Instance Method Details

#directory ⇒ Object

Return an array of row offsets for all entries in the page directory.



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# File 'lib/innodb/page/index.rb', line 657

def directory
  return @directory if @directory

  @directory = []
  cursor(pos_directory).backward.name("page_directory") do |c|
    directory_slots.times do |n|
      @directory.push c.name("slot[#{n}]") { c.get_uint16 }
    end
  end

  @directory
end

#directory_slots ⇒ Object

The number of directory slots in use.



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# File 'lib/innodb/page/index.rb', line 169

def directory_slots
  page_header[:n_dir_slots]
end

#directory_space ⇒ Object

The amount of space consumed by the page directory.



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# File 'lib/innodb/page/index.rb', line 174

def directory_space
  directory_slots * PAGE_DIR_SLOT_SIZE
end

#dump ⇒ Object

Dump the contents of a page for debugging purposes.



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# File 'lib/innodb/page/index.rb', line 671

def dump
  super

  puts "page header:"
  pp page_header
  puts

  puts "fseg header:"
  pp fseg_header
  puts

  puts "sizes:"
  puts "  %-15s%5i" % [ "header",     header_space ]
  puts "  %-15s%5i" % [ "trailer",    trailer_space ]
  puts "  %-15s%5i" % [ "directory",  directory_space ]
  puts "  %-15s%5i" % [ "free",       free_space ]
  puts "  %-15s%5i" % [ "used",       used_space ]
  puts "  %-15s%5i" % [ "record",     record_space ]
  puts "  %-15s%5.2f" % [
    "per record",
    (page_header[:n_recs] > 0) ? (record_space / page_header[:n_recs]) : 0
  ]
  puts

  puts "page directory:"
  pp directory
  puts

  puts "system records:"
  pp infimum.record
  pp supremum.record
  puts

  puts "garbage records:"
  each_garbage_record do |rec|
    pp rec.record
    puts
  end
  puts

  puts "records:"
  each_record do |rec|
    pp rec.record
    puts
  end
  puts
end

#each_child_page ⇒ Object

Iterate through all child pages of a node (non-leaf) page, which are stored as records with the child page number as the last field in the record.



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# File 'lib/innodb/page/index.rb', line 642

def each_child_page
  return nil if level == 0

  unless block_given?
    return enum_for(:each_child_page)
  end

  each_record do |rec|
    yield rec.child_page_number, rec.key
  end

  nil
end

#each_garbage_record ⇒ Object 



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# File 'lib/innodb/page/index.rb', line 621

def each_garbage_record
  unless block_given?
    return enum_for(:each_garbage_record)
  end

  if garbage_offset == 0
    return nil
  end

  c = record_cursor(garbage_offset)

  while rec = c.record
    yield rec
  end

  nil
end

#each_record ⇒ Object

Iterate through all records.



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# File 'lib/innodb/page/index.rb', line 607

def each_record
  unless block_given?
    return enum_for(:each_record)
  end

  c = record_cursor(infimum.next)

  while rec = c.record
    yield rec
  end

  nil
end

#first_record ⇒ Object

Return the first record on this page.



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# File 'lib/innodb/page/index.rb', line 601

def first_record
  first = record(infimum.next)
  first if first != supremum
end

#free_space ⇒ Object

Return the amount of free space in the page.



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# File 'lib/innodb/page/index.rb', line 184

def free_space
  page_header[:garbage_size] +
    (size - size_fil_trailer - directory_space - page_header[:heap_top])
end

#fseg_header ⇒ Object

Return the "fseg" header.



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# File 'lib/innodb/page/index.rb', line 254

def fseg_header
  @fseg_header ||= cursor(pos_fseg_header).name("fseg") do |c|
    {
      :leaf     => c.name("fseg[leaf]") {
        Innodb::FsegEntry.get_inode(@space, c)
      },
      :internal => c.name("fseg[internal]") {
        Innodb::FsegEntry.get_inode(@space, c)
      },
    }
  end
end

#garbage_offset ⇒ Object

A helper function to return the offset to the first free record.



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# File 'lib/innodb/page/index.rb', line 249

def garbage_offset
  page_header && page_header[:garbage_offset]
end

#header_space ⇒ Object

The amount of space consumed by the page header.



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# File 'lib/innodb/page/index.rb', line 162

def header_space
  # The end of the supremum system record is the beginning of the space
  # available for user records.
  pos_user_records
end

#infimum ⇒ Object

Return the infimum record on a page.



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# File 'lib/innodb/page/index.rb', line 442

def infimum
  @infimum ||= system_record(pos_infimum)
end

#level ⇒ Object

A helper function to return the page level from the "page" header, for easier access.



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# File 'lib/innodb/page/index.rb', line 233

def level
  page_header && page_header[:level]
end

#make_record_description ⇒ Object

Return a set of field objects that describe the record.



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# File 'lib/innodb/page/index.rb', line 452

def make_record_description
  description = record_describer.description

  position = 0
  fields = {:type => description[:type], :key => [], :row => []}

  description[:key].each do |field|
    fields[:key] << Innodb::Field.new(position, field[:name], *field[:type])
    position += 1
  end

  if description[:type] == :clustered
    # Account for TRX_ID and ROLL_PTR.
    position += 2
  end

  description[:row].each do |field|
    fields[:row] << Innodb::Field.new(position, field[:name], *field[:type])
    position += 1
  end

  fields
end

#page_header ⇒ Object

Return the "index" header.



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# File 'lib/innodb/page/index.rb', line 206

def page_header
  @page_header ||= cursor(pos_index_header).name("index") do |c|
    index = {
      :n_dir_slots            => c.name("n_dir_slots") { c.get_uint16 },
      :heap_top               => c.name("heap_top") { c.get_uint16 },
      :n_heap_format          => c.name("n_heap_format") { c.get_uint16 },
      :garbage_offset         => c.name("garbage_offset") { c.get_uint16 },
      :garbage_size           => c.name("garbage_size") { c.get_uint16 },
      :last_insert_offset     => c.name("last_insert_offset") { c.get_uint16 },
      :direction              => c.name("direction") { PAGE_DIRECTION[c.get_uint16] },
      :n_direction            => c.name("n_direction") { c.get_uint16 },
      :n_recs                 => c.name("n_recs") { c.get_uint16 },
      :max_trx_id             => c.name("max_trx_id") { c.get_uint64 },
      :level                  => c.name("level") { c.get_uint16 },
      :index_id               => c.name("index_id") { c.get_uint64 },
    }
    index[:n_heap] = index[:n_heap_format] & (2**15-1)
    index[:format] = (index[:n_heap_format] & 1<<15) == 0 ?
      :redundant : :compact
    index.delete :n_heap_format

    index
  end
end

#pos_directory ⇒ Object

The position of the page directory, which starts at the "fil" trailer and grows backwards from there.



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# File 'lib/innodb/page/index.rb', line 157

def pos_directory
  pos_fil_trailer
end

#pos_fseg_header ⇒ Object

Return the byte offset of the start of the "fseg" header, which immediately follows the "index" header.



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# File 'lib/innodb/page/index.rb', line 83

def pos_fseg_header
  pos_index_header + size_index_header
end

#pos_index_header ⇒ Object

Return the byte offset of the start of the "index" page header, which immediately follows the "fil" header.



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# File 'lib/innodb/page/index.rb', line 72

def pos_index_header
  pos_fil_header + size_fil_header
end

#pos_infimum ⇒ Object

Return the byte offset of the start of the "origin" of the infimum record, which is always the first record in the singly-linked record chain on any page, and represents a record with a "lower value than any possible user record". The infimum record immediately follows the page header.



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# File 'lib/innodb/page/index.rb', line 124

def pos_infimum
  pos_records +
    size_record_header +
    size_mum_record_header_additional
end

#pos_records ⇒ Object

Return the byte offset of the start of records within the page (the position immediately after the page header).



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# File 'lib/innodb/page/index.rb', line 143

def pos_records
  size_fil_header +
    size_index_header +
    size_fseg_header
end

#pos_supremum ⇒ Object

Return the byte offset of the start of the "origin" of the supremum record, which is always the last record in the singly-linked record chain on any page, and represents a record with a "higher value than any possible user record". The supremum record immediately follows the infimum record.



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

def pos_supremum
  pos_infimum +
    size_record_header +
    size_mum_record_header_additional +
    size_mum_record
end

#pos_user_records ⇒ Object

Return the byte offset of the start of the user records in a page, which immediately follows the supremum record.



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# File 'lib/innodb/page/index.rb', line 151

def pos_user_records
  pos_supremum + size_mum_record
end

#record(offset) ⇒ Object

Parse and return a record at a given offset.



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# File 'lib/innodb/page/index.rb', line 484

def record(offset)
  return nil unless offset
  return infimum  if offset == pos_infimum
  return supremum if offset == pos_supremum

  cursor(offset).forward.name("record[#{offset}]") do |c|
    # There is a header preceding the row itself, so back up and read it.
    header = c.peek { record_header(c) }

    this_record = {
      :format => page_header[:format],
      :offset => offset,
      :header => header,
      :next => header[:next] == 0 ? nil : (header[:next]),
    }

    if record_format
      this_record[:type] = record_format[:type]

      # Read the key fields present in all types of pages.
      this_record[:key] = []
      record_format[:key].each do |f|
        c.name("key[#{f.name}]") do
          this_record[:key] << {
            :name => f.name,
            :type => f.data_type.name,
            :value => f.value(this_record, c),
            :extern => f.extern(this_record, c),
          }
        end
      end

      # If this is a leaf page of the clustered index, read InnoDB's internal
      # fields, a transaction ID and roll pointer.
      if level == 0 && record_format[:type] == :clustered
        this_record[:transaction_id] = c.name("transaction_id") { c.get_hex(6) }
        c.name("roll_pointer") do
          rseg_id_insert_flag = c.name("rseg_id_insert_flag") { c.get_uint8 }
          this_record[:roll_pointer]   = {
            :is_insert  => (rseg_id_insert_flag & 0x80) == 0x80,
            :rseg_id    => rseg_id_insert_flag & 0x7f,
            :undo_log   => c.name("undo_log") {
              {
                :page   => c.name("page")   { c.get_uint32 },
                :offset => c.name("offset") { c.get_uint16 },
              }
            }
          }
        end
      end

      # If this is a leaf page of the clustered index, or any page of a
      # secondary index, read the non-key fields.
      if (level == 0 && record_format[:type] == :clustered) ||
        (record_format[:type] == :secondary)
        # Read the non-key fields.
        this_record[:row] = []
        record_format[:row].each do |f|
          c.name("row[#{f.name}]") do
            this_record[:row] << {
              :name => f.name,
              :type => f.data_type.name,
              :value => f.value(this_record, c),
              :extern => f.extern(this_record, c),
            }
          end
        end
      end

      # If this is a node (non-leaf) page, it will have a child page number
      # (or "node pointer") stored as the last field.
      if level > 0
        # Read the node pointer in a node (non-leaf) page.
        this_record[:child_page_number] =
          c.name("child_page_number") { c.get_uint32 }
      end
    end

    Innodb::Record.new(this_record)
  end
end

#record_bytes ⇒ Object

Return the actual bytes of the portion of the page which is used to store user records (eliminate the headers and trailer from the page).



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# File 'lib/innodb/page/index.rb', line 201

def record_bytes
  data(pos_user_records, page_header[:heap_top] - pos_user_records)
end

#record_cursor(offset) ⇒ Object

Return a RecordCursor starting at offset.



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# File 'lib/innodb/page/index.rb', line 596

def record_cursor(offset)
  RecordCursor.new(self, offset)
end

#record_format ⇒ Object

Return (and cache) the record format provided by an external class.



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# File 'lib/innodb/page/index.rb', line 477

def record_format
  if record_describer
    @record_format ||= make_record_description()
  end
end

#record_header(cursor) ⇒ Object

Return the header from a record.



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# File 'lib/innodb/page/index.rb', line 268

def record_header(cursor)
  origin = cursor.position
  header = {}
  cursor.backward.name("header") do |c|
    case page_header[:format]
    when :compact
      # The "next" pointer is a relative offset from the current record.
      header[:next] = c.name("next") { origin + c.get_sint16 }

      # Fields packed in a 16-bit integer (LSB first):
      #   3 bits for type
      #   13 bits for heap_number
      bits1 = c.name("bits1") { c.get_uint16 }
      header[:type] = RECORD_TYPES[bits1 & 0x07]
      header[:heap_number] = (bits1 & 0xf8) >> 3
    when :redundant
      # The "next" pointer is an absolute offset within the page.
      header[:next] = c.name("next") { c.get_uint16 }

      # Fields packed in a 24-bit integer (LSB first):
      #   1 bit for offset_size (0 = 2 bytes, 1 = 1 byte)
      #   10 bits for n_fields
      #   13 bits for heap_number
      bits1 = c.name("bits1") { c.get_uint24 }
      header[:offset_size]  = (bits1 & 1) == 0 ? 2 : 1
      header[:n_fields]     = (bits1 & (((1 << 10) - 1) <<  1)) >>  1
      header[:heap_number]  = (bits1 & (((1 << 13) - 1) << 11)) >> 11
    end

    # Fields packed in an 8-bit integer (LSB first):
    #   4 bits for n_owned
    #   4 bits for flags
    bits2 = c.name("bits2") { c.get_uint8 }
    header[:n_owned] = bits2 & 0x0f
    info = (bits2 & 0xf0) >> 4
    header[:min_rec] = (info & RECORD_INFO_MIN_REC_FLAG) != 0
    header[:deleted] = (info & RECORD_INFO_DELETED_FLAG) != 0

    case page_header[:format]
    when :compact
      record_header_compact_additional(header, cursor)
    when :redundant
      record_header_redundant_additional(header, cursor)
    end
  end

  header
end

#record_header_compact_additional(header, cursor) ⇒ Object

Read additional header information from a compact format record header.



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# File 'lib/innodb/page/index.rb', line 318

def record_header_compact_additional(header, cursor)
  case header[:type]
  when :conventional, :node_pointer
    # The variable-length part of the record header contains a
    # bit vector indicating NULL fields and the length of each
    # non-NULL variable-length field.
    if record_format
      header[:field_nulls] = cursor.name("field_nulls") {
        record_header_compact_null_bitmap(cursor)
      }
      header[:field_lengths], header[:field_externs] =
        cursor.name("field_lengths_and_externs") {
          record_header_compact_variable_lengths_and_externs(cursor,
            header[:field_nulls])
        }
    end
  end
end

#record_header_compact_null_bitmap(cursor) ⇒ Object

Return an array indicating which fields are null.



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# File 'lib/innodb/page/index.rb', line 338

def record_header_compact_null_bitmap(cursor)
  fields = (record_format[:key] + record_format[:row])

  # The number of bits in the bitmap is the number of nullable fields.
  size = fields.count { |f| f.nullable? }

  # There is no bitmap if there are no nullable fields.
  return nil unless size > 0

  # To simplify later checks, expand bitmap to one for each field.
  bitmap = Array.new(fields.last.position + 1, false)

  null_bit_array = cursor.get_bit_array(size).reverse!

  # For every nullable field, set whether the field is actually null.
  fields.each do |f|
    bitmap[f.position] = f.nullable? ? (null_bit_array.shift == 1) : false
  end

  return bitmap
end

#record_header_compact_variable_lengths_and_externs(cursor, null_bitmap) ⇒ Object

Return an array containing an array of the length of each variable-length field and an array indicating which fields are stored externally.



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# File 'lib/innodb/page/index.rb', line 362

def record_header_compact_variable_lengths_and_externs(cursor, null_bitmap)
  fields = (record_format[:key] + record_format[:row])

  len_array = Array.new(fields.last.position + 1, 0)
  ext_array = Array.new(fields.last.position + 1, false)

  # For each non-NULL variable-length field, the record header contains
  # the length in one or two bytes.
  fields.each do |f|
    next if !f.variable? or (null_bitmap && null_bitmap[f.position])

    len = cursor.get_uint8
    ext = false

    # Two bytes are used only if the length exceeds 127 bytes and the
    # maximum length exceeds 255 bytes (or the field is a BLOB type).
    if len > 127 && (f.blob? || f.data_type.width > 255)
      ext = (0x40 & len) != 0
      len = ((len & 0x3f) << 8) + cursor.get_uint8
    end

    len_array[f.position] = len
    ext_array[f.position] = ext
  end

  return len_array, ext_array
end

#record_header_redundant_additional(header, cursor) ⇒ Object

Read additional header information from a redundant format record header.



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# File 'lib/innodb/page/index.rb', line 391

def record_header_redundant_additional(header, cursor)
  header[:field_lengths] = []
  header[:field_nulls] = []
  header[:field_externs] = []

  field_offsets = record_header_redundant_field_end_offsets(header, cursor)

  this_field_offset = 0
  field_offsets.each do |n|
    case header[:offset_size]
    when 1
      next_field_offset = (n & RECORD_REDUNDANT_OFF1_OFFSET_MASK)
      header[:field_lengths]  << (next_field_offset - this_field_offset)
      header[:field_nulls]    << ((n & RECORD_REDUNDANT_OFF1_NULL_MASK) != 0)
      header[:field_externs]  << false
    when 2
      next_field_offset = (n & RECORD_REDUNDANT_OFF2_OFFSET_MASK)
      header[:field_lengths]  << (next_field_offset - this_field_offset)
      header[:field_nulls]    << ((n & RECORD_REDUNDANT_OFF2_NULL_MASK) != 0)
      header[:field_externs]  << ((n & RECORD_REDUNDANT_OFF2_EXTERN_MASK) != 0)
    end
    this_field_offset = next_field_offset
  end
end

#record_header_redundant_field_end_offsets(header, cursor) ⇒ Object

Read field end offsets from the provided cursor for each field as counted by n_fields.



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# File 'lib/innodb/page/index.rb', line 418

def record_header_redundant_field_end_offsets(header, cursor)
  (0...header[:n_fields]).to_a.inject([]) do |offsets, n|
    cursor.name("field_end_offset[#{n}]") {
      offsets << cursor.get_uint_by_size(header[:offset_size])
    }
    offsets
  end
end

#record_space ⇒ Object

Return the amount of space occupied by records in the page.



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# File 'lib/innodb/page/index.rb', line 195

def record_space
  used_space - header_space - directory_space - trailer_space
end

#records ⇒ Object

A helper function to return the number of records.



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# File 'lib/innodb/page/index.rb', line 238

def records
  page_header && page_header[:n_recs]
end

#root? ⇒ Boolean

A helper function to identify root index pages; they must be the only pages at their level.

Returns:

  • (Boolean) 


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# File 'lib/innodb/page/index.rb', line 244

def root?
  self.prev.nil? && self.next.nil?
end

#size_fseg_header ⇒ Object

The size of the "fseg" header.



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# File 'lib/innodb/page/index.rb', line 88

def size_fseg_header
  2 * Innodb::FsegEntry::SIZE
end

#size_index_header ⇒ Object

The size of the "index" header.



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# File 'lib/innodb/page/index.rb', line 77

def size_index_header
  2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 2 + 8 + 2 + 8
end

#size_mum_record ⇒ Object

The size of the data from the supremum or infimum records.



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# File 'lib/innodb/page/index.rb', line 116

def size_mum_record
  8
end

#size_mum_record_header_additional ⇒ Object

The size of the additional data structures in the header of the system records, which is just 1 byte in redundant format to store the offset of the end of the field. This is needed specifically here since we need to be able to calculate the fixed positions of these system records.



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# File 'lib/innodb/page/index.rb', line 106

def size_mum_record_header_additional
  case page_header[:format]
  when :compact
    0 # No additional data is stored in compact format.
  when :redundant
    1 # A 1-byte offset for 1 field is stored in redundant format.
  end
end

#size_record_header ⇒ Object

Return the size of the header for each record.



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# File 'lib/innodb/page/index.rb', line 93

def size_record_header
  case page_header[:format]
  when :compact
    RECORD_NEXT_SIZE + RECORD_COMPACT_BITS_SIZE
  when :redundant
    RECORD_NEXT_SIZE + RECORD_REDUNDANT_BITS_SIZE
  end
end

#supremum ⇒ Object

Return the supremum record on a page.



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# File 'lib/innodb/page/index.rb', line 447

def supremum
  @supremum ||= system_record(pos_supremum)
end

#system_record(offset) ⇒ Object

Parse and return simple fixed-format system records, such as InnoDB's internal infimum and supremum records.



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# File 'lib/innodb/page/index.rb', line 429

def system_record(offset)
  cursor(offset).name("record[#{offset}]") do |c|
    header = c.peek { record_header(c) }
    Innodb::Record.new({
      :offset => offset,
      :header => header,
      :next => header[:next],
      :data => c.name("data") { c.get_bytes(size_mum_record) },
    })
  end
end

#trailer_space ⇒ Object

The amount of space consumed by the trailers in the page.



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# File 'lib/innodb/page/index.rb', line 179

def trailer_space
  size_fil_trailer
end

#used_space ⇒ Object

Return the amount of used space in the page.



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# File 'lib/innodb/page/index.rb', line 190

def used_space
  size - free_space
end