Class: Innodb::Index::IndexCursor

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

Overview

A cursor to walk the index (cursor) forwards or backward starting with a given record, or the minimum (:min) or maximum (:max) record in the index.

Instance Method Summary collapse

Constructor Details

#initialize(index, record, direction) ⇒ IndexCursor

Returns a new instance of IndexCursor.



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# File 'lib/innodb/index.rb', line 243

def initialize(index, record, direction)
  Innodb::Stats.increment :index_cursor_create
  @index = index
  @direction = direction
  case record
  when :min
    # Start at the minimum record on the minimum page in the index.
    @page = index.min_page_at_level(0)
    @page_cursor = @page.record_cursor(:min, direction)
  when :max
    # Start at the maximum record on the maximum page in the index.
    @page = index.max_page_at_level(0)
    @page_cursor = @page.record_cursor(:max, direction)
  else
    # Start at the record provided.
    @page = record.page
    @page_cursor = @page.record_cursor(record.offset, direction)
  end
end

Instance Method Details

#each_record ⇒ Object

Iterate through all records in the cursor.



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# File 'lib/innodb/index.rb', line 278

def each_record
  return enum_for(:each_record) unless block_given?

  while (rec = record)
    yield rec
  end
end

#record ⇒ Object

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



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# File 'lib/innodb/index.rb', line 264

def record
  if (rec = @page_cursor.record)
    return rec
  end

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