Module: RR::TableScanHelper

Included in:
DirectTableScan, ProxyBlockCursor, TableScan
Defined in:
lib/rubyrep/table_scan_helper.rb

Overview

Some helper functions that are of use to all TableScan classes

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.scan_class(session) ⇒ Object

Returns the correct class for the table scan based on the type of the session (proxied or direct).



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# File 'lib/rubyrep/table_scan_helper.rb', line 38

def self.scan_class(session)
  if session.proxied?
    ProxiedTableScan
  else
    DirectTableScan
  end
end

Instance Method Details

#rank_rows(left_row, right_row) ⇒ Object

Compares the primary keys of left_row and right_row to determine their rank. Assumes there is a function primary_key_names returning the array of primary keys that are relevant for this comparison

Assumes that at least one of left_row and right_row is not nil A nil row counts as infinite.

    1. left_row is something and right_row is nil ==> left_row is smaller ==> return -1



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# File 'lib/rubyrep/table_scan_helper.rb', line 16

def rank_rows(left_row, right_row)
  raise "At least one of left_row and right_row must not be nil!" unless left_row or right_row
  return -1 unless right_row
  return 1 unless left_row 
  rank = 0
  primary_key_names.any? do |key|
    if left_row[key].kind_of?(String)
      # When databases order strings, then 'a' < 'A' while for Ruby 'A' < 'a'
      # ==> Use a combination of case sensitive and case insensitive comparing to
      #     reproduce the database behaviour.
      rank = left_row[key].casecmp(right_row[key]) # deal with 'a' to 'B' comparisons
      rank = -(left_row[key] <=> right_row[key]) if rank == 0 # deal with 'a' to 'A' comparisons
    else
      rank = left_row[key] <=> right_row[key]
    end
    rank != 0
  end
  rank
end