Class: RR::DirectTableScan

Inherits:
TableScan show all
Includes:
TableScanHelper
Defined in:
lib/rubyrep/direct_table_scan.rb

Overview

Scans two tables for differences. Doesn’t have any reporting functionality by itself. Instead DirectTableScan#run yields all the differences for the caller to do with as it pleases. Usage:

1. Create a new DirectTableScan object and hand it all necessary information
2. Call DirectTableScan#run to do the actual comparison
3. The block handed to DirectTableScan#run receives all differences

Instance Attribute Summary collapse

Attributes inherited from TableScan

#left_table, #primary_key_names, #progress_printer, #right_table, #session

Instance Method Summary collapse

Methods included from TableScanHelper

#rank_rows, scan_class

Methods inherited from TableScan

#scan_options, #update_progress

Constructor Details

#initialize(session, left_table, right_table = nil) ⇒ DirectTableScan

Creates a new DirectTableScan instance

* session: a Session object representing the current database session
* left_table: name of the table in the left database
* right_table: name of the table in the right database. If not given, same like left_table



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# File 'lib/rubyrep/direct_table_scan.rb', line 23

def initialize(session, left_table, right_table = nil)
  super
end

Instance Attribute Details

#left_caster ⇒ Object

The TypeCastingCursor for the left table



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# File 'lib/rubyrep/direct_table_scan.rb', line 14

def left_caster
  @left_caster
end

#right_caster ⇒ Object

The TypeCastingCursor for the right table



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# File 'lib/rubyrep/direct_table_scan.rb', line 17

def right_caster
  @right_caster
end

Instance Method Details

#run(&blck) ⇒ Object

Runs the table scan. Calls the block for every found difference. Differences are yielded with 2 parameters

* type: describes the difference, either :left (row only in left table), :right (row only in right table) or :conflict
* row: For :left or :right cases a hash describing the row; for :conflict an array of left and right row.
       A row is a hash of column_name => value pairs.



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# File 'lib/rubyrep/direct_table_scan.rb', line 33

def run(&blck)
  left_cursor = right_cursor = nil
  left_cursor = session.left.select_cursor(
    :table => left_table,
    :row_buffer_size => scan_options[:row_buffer_size],
    :type_cast => true
  )
  right_cursor = session.right.select_cursor(
    :table => right_table,
    :row_buffer_size => scan_options[:row_buffer_size],
    :type_cast => true
  )
  left_row = right_row = nil
  update_progress 0 # ensures progress bar is printed even if there are no records
  while left_row or right_row or left_cursor.next? or right_cursor.next?
    # if there is no current left row, _try_ to load the next one
    left_row ||= left_cursor.next_row if left_cursor.next?
    # if there is no current right row, _try_ to load the next one
    right_row ||= right_cursor.next_row if right_cursor.next?
    rank = rank_rows left_row, right_row
    case rank
    when -1
      yield :left, left_row
      left_row = nil
      update_progress 1
    when 1
      yield :right, right_row
      right_row = nil
      update_progress 1
    when 0
      update_progress 2
      if not left_row == right_row
        yield :conflict, [left_row, right_row]
      end
      left_row = right_row = nil
    end
    # check for corresponding right rows
  end
ensure
  [left_cursor, right_cursor].each {|cursor| cursor.clear if cursor}
end