Class: Innodb::Page::Index::RecordCursor

Inherits:

Object

• Object
• Innodb::Page::Index::RecordCursor

Defined in:

lib/innodb/page/index.rb

Overview

A class for cursoring through records starting from an arbitrary point.

Instance Method Summary

• #each_record ⇒ Object

  Iterate through all records in the cursor.

• #initialize(page, offset, direction) ⇒ RecordCursor constructor

  A new instance of RecordCursor.

• #next_record ⇒ Object

  Return the next record, and advance the cursor.

• #prev_record ⇒ Object

  Return the previous record, and advance the cursor.

• #record ⇒ Object

  Return the next record in the order defined when the cursor was created.

Constructor Details

#initialize(page, offset, direction) ⇒ RecordCursor

Returns a new instance of RecordCursor.

# File 'lib/innodb/page/index.rb', line 644

def initialize(page, offset, direction)
  Innodb::Stats.increment :page_record_cursor_create

  @initial = true
  @page = page
  @direction = direction
  case offset
  when :min
    @record = @page.min_record
  when :max
    @record = @page.max_record
  else
    # Offset is a byte offset of a record (hopefully).
    @record = @page.record(offset)
  end
end

Instance Method Details

#each_record ⇒ Object

Iterate through all records in the cursor.

# File 'lib/innodb/page/index.rb', line 717

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

  while rec = record
    yield rec
  end
end

#next_record ⇒ Object

Return the next record, and advance the cursor. Return nil when the end of records (supremum) is reached.

# File 'lib/innodb/page/index.rb', line 663

def next_record
  Innodb::Stats.increment :page_record_cursor_next_record

  rec = @page.record(@record.next)

  # The garbage record list's end is self-linked, so we must check for
  # both supremum and the current record's offset.
  if rec == @page.supremum || rec.offset == @record.offset
    # We've reached the end of the linked list at supremum.
    nil
  else
    @record = rec
  end
end

#prev_record ⇒ Object

Return the previous record, and advance the cursor. Return nil when the end of records (infimum) is reached.

# File 'lib/innodb/page/index.rb', line 680

def prev_record
  Innodb::Stats.increment :page_record_cursor_prev_record

  unless slot = @page.directory_slot_for_record(@record)
    raise "Couldn't find slot for record"
  end

  unless search_cursor = @page.record_cursor(@page.directory[slot-1])
    raise "Couldn't position search cursor"
  end

  while rec = search_cursor.record and rec.offset != @record.offset
    if rec.next == @record.offset
      if rec == @page.infimum
        return nil
      end
      return @record = rec
    end
  end
end

#record ⇒ Object

Return the next record in the order defined when the cursor was created.

# File 'lib/innodb/page/index.rb', line 702

def record
  if @initial
    @initial = false
    return @record
  end

  case @direction
  when :forward
    next_record
  when :backward
    prev_record
  end
end