Class: Innodb::Index

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

Defined Under Namespace

Classes: IndexCursor

Constant Summary collapse

FSEG_LIST_NAMES = 
%i[
  internal
  leaf
].freeze

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(space, root_page_number, record_describer = nil) ⇒ Index

Returns a new instance of Index.



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# File 'lib/innodb/index.rb', line 15

def initialize(space, root_page_number, record_describer = nil)
  @space = space
  @record_describer = record_describer || space.record_describer

  @root = page(root_page_number)

  raise "Page #{root_page_number} couldn't be read" unless @root

  # The root page should be an index page.
  unless @root.is_a?(Innodb::Page::Index)
    raise "Page #{root_page_number} is a #{@root.type} page, not an INDEX page"
  end

  # The root page should be the only page at its level.
  raise "Page #{root_page_number} does not appear to be an index root" if @root.prev || @root.next
end

Instance Attribute Details

#record_describer ⇒ Object

Returns the value of attribute record_describer.



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

def record_describer
  @record_describer
end

#root ⇒ Object (readonly)

Returns the value of attribute root.



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

def root
  @root
end

#space ⇒ Object (readonly)

Returns the value of attribute space.



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# File 'lib/innodb/index.rb', line 7

def space
  @space
end

Instance Method Details

#_recurse(parent_page, page_proc, link_proc, depth = 0) ⇒ Object

Internal method used by recurse.



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# File 'lib/innodb/index.rb', line 57

def _recurse(parent_page, page_proc, link_proc, depth = 0)
  page_proc.call(parent_page, depth) if page_proc && parent_page.is_a?(Innodb::Page::Index)

  parent_page.each_child_page do |child_page_number, child_min_key|
    child_page = page(child_page_number)
    child_page.record_describer = record_describer
    next unless child_page.is_a?(Innodb::Page::Index)

    link_proc&.call(parent_page, child_page, child_min_key, depth + 1)
    _recurse(child_page, page_proc, link_proc, depth + 1)
  end
end

#binary_search(key) ⇒ Object

Search for a record within the entire index like linear_search, but use the page directory to search while making as few record comparisons as possible. If a matching record is not found, nil is returned.



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# File 'lib/innodb/index.rb', line 210

def binary_search(key)
  Innodb::Stats.increment :binary_search

  page = @root

  if Innodb.debug?
    puts "binary_search: root=%i, level=%i, key=(%s)" % [
      page.offset,
      page.level,
      key.join(", "),
    ]
  end

  # Remove supremum from the page directory, since nothing can be scanned
  # linearly from there anyway.
  while (rec = page.binary_search_by_directory(page.directory[0...-1], key))
    if page.level.positive?
      # If we haven't reached a leaf page yet, move down the tree and search
      # again using binary search.
      page = page(rec.child_page_number)
    else
      # We're on a leaf page, so return the page and record if there is a
      # match. If there is no match, break the loop and cause nil to be
      # returned.
      return rec if rec.compare_key(key).zero?

      break
    end
  end
end

#cursor(record = :min, direction = :forward) ⇒ Object

Return an IndexCursor starting at the given record (an Innodb::Record, :min, or :max) and cursor in the direction given (:forward or :backward).



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# File 'lib/innodb/index.rb', line 329

def cursor(record = :min, direction = :forward)
  IndexCursor.new(self, record, direction)
end

#each_fseg ⇒ Object

Iterate through all file segments in the index.



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# File 'lib/innodb/index.rb', line 120

def each_fseg
  return enum_for(:each_fseg) unless block_given?

  FSEG_LIST_NAMES.each do |fseg_name|
    yield fseg_name, fseg(fseg_name)
  end
end

#each_fseg_frag_page(fseg) ⇒ Object

Iterate through all frag pages in a given fseg.



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# File 'lib/innodb/index.rb', line 136

def each_fseg_frag_page(fseg)
  return enum_for(:each_fseg_frag_page, fseg) unless block_given?

  fseg.frag_array_pages.each do |page_number|
    yield page_number, page(page_number)
  end
end

#each_fseg_list(fseg, &block) ⇒ Object

Iterate through all lists in a given fseg.



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# File 'lib/innodb/index.rb', line 129

def each_fseg_list(fseg, &block)
  return enum_for(:each_fseg_list, fseg) unless block_given?

  fseg.each_list(&block)
end

#each_page_at_level(level, &block) ⇒ Object

Iterate through all pages at the given level by finding the first page and following the next pointers in each page.



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# File 'lib/innodb/index.rb', line 158

def each_page_at_level(level, &block)
  return enum_for(:each_page_at_level, level) unless block_given?

  each_page_from(min_page_at_level(level), &block)
end

#each_page_from(page) ⇒ Object

Iterate through all pages at this level starting with the provided page.



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

def each_page_from(page)
  return enum_for(:each_page_from, page) unless block_given?

  while page.is_a?(Innodb::Page::Index)
    yield page
    break unless page.next

    page = page(page.next)
  end
end

#each_record(&block) ⇒ Object

Iterate through all records on all leaf pages in ascending order.



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# File 'lib/innodb/index.rb', line 165

def each_record(&block)
  return enum_for(:each_record) unless block_given?

  each_page_at_level(0) do |page|
    page.each_record(&block)
  end
end

#field_names ⇒ Object 



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# File 'lib/innodb/index.rb', line 115

def field_names
  record_describer.field_names
end

#fseg(name) ⇒ Object

Return the file segment with the given name from the fseg header.



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# File 'lib/innodb/index.rb', line 111

def fseg(name)
  @root.fseg_header[name]
end

#id ⇒ Object

A helper function to access the index ID in the page header.



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# File 'lib/innodb/index.rb', line 41

def id
  @root.page_header.index_id
end

#linear_search(key) ⇒ Object

Search for a record within the entire index, walking down the non-leaf pages until a leaf page is found, and then verifying that the record returned on the leaf page is an exact match for the key. If a matching record is not found, nil is returned (either because linear_search_in_page returns nil breaking the loop, or because compare_key returns non-zero).



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# File 'lib/innodb/index.rb', line 178

def linear_search(key)
  Innodb::Stats.increment :linear_search

  page = @root

  if Innodb.debug?
    puts "linear_search: root=%i, level=%i, key=(%s)" % [
      page.offset,
      page.level,
      key.join(", "),
    ]
  end

  while (rec = page.linear_search_from_cursor(page.record_cursor(page.infimum.next), key))
    if page.level.positive?
      # If we haven't reached a leaf page yet, move down the tree and search
      # again using linear search.
      page = page(rec.child_page_number)
    else
      # We're on a leaf page, so return the page and record if there is a
      # match. If there is no match, break the loop and cause nil to be
      # returned.
      return rec if rec.compare_key(key).zero?

      break
    end
  end
end

#max_page_at_level(level) ⇒ Object

Return the last leaf page in the index by walking down the right side of the B-tree until a page at the given level is encountered.



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

def max_page_at_level(level)
  page = @root
  record = @root.max_record
  while record && page.level > level
    page = page(record.child_page_number)
    record = page.max_record
  end
  page if page.level == level
end

#max_record ⇒ Object

Return the maximum record in the index.



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

def max_record
  max_page_at_level(0)&.max_record
end

#min_page_at_level(level) ⇒ Object

Return the first leaf page in the index by walking down the left side of the B-tree until a page at the given level is encountered.



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# File 'lib/innodb/index.rb', line 78

def min_page_at_level(level)
  page = @root
  record = @root.min_record
  while record && page.level > level
    page = page(record.child_page_number)
    record = page.min_record
  end
  page if page.level == level
end

#min_record ⇒ Object

Return the minimum record in the index.



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# File 'lib/innodb/index.rb', line 89

def min_record
  min_page_at_level(0)&.min_record
end

#node_type(page) ⇒ Object

Return the type of node that the given page represents in the index tree.



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# File 'lib/innodb/index.rb', line 46

def node_type(page)
  if @root.offset == page.offset
    :root
  elsif page.level.zero?
    :leaf
  else
    :internal
  end
end

#page(page_number) ⇒ Object 



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# File 'lib/innodb/index.rb', line 32

def page(page_number)
  page = @space.page(page_number)
  raise "Page #{page_number} couldn't be read" unless page

  page.record_describer = @record_describer
  page
end

#recurse(page_proc, link_proc) ⇒ Object

Walk an index tree depth-first, calling procs for each page and link in the tree.



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

def recurse(page_proc, link_proc)
  _recurse(@root, page_proc, link_proc)
end