Module: ArJdbc::MsSQL::LimitHelpers::SqlServer2000ReplaceLimitOffset

Included in:
Arel::Visitors::SQLServer2000
Defined in:
lib/arjdbc/mssql/limit_helpers.rb

Class Method Summary collapse

Class Method Details

.replace_limit_offset!(sql, limit, offset, order) ⇒ Object 



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# File 'lib/arjdbc/mssql/limit_helpers.rb', line 17

def replace_limit_offset!(sql, limit, offset, order)
  if limit
    offset ||= 0
    start_row = offset + 1
    end_row = offset + limit.to_i
    find_select = /\b(SELECT(?:\s+DISTINCT)?)\b(.*)/im
    whole, select, rest_of_query = find_select.match(sql).to_a
    if (start_row == 1) && (end_row ==1)
      new_sql = "#{select} TOP 1 #{rest_of_query}"
      sql.replace(new_sql)
    else
      #UGLY
      #KLUDGY?
      #removing out stuff before the FROM...
      rest = rest_of_query[/FROM/i=~ rest_of_query.. -1]
      #need the table name for avoiding amiguity
      table_name = LimitHelpers.get_table_name(sql)
      primary_key = order[/(\w*id\w*)/i]
      #I am not sure this will cover all bases.  but all the tests pass
      new_order = "ORDER BY #{order}, #{table_name}.#{primary_key}" if order.index("#{table_name}.#{primary_key}").nil?
      new_order ||= order

      if (rest_of_query.match(/WHERE/).nil?)
        new_sql = "#{select} TOP #{limit} #{rest_of_query} WHERE #{table_name}.#{primary_key} NOT IN (#{select} TOP #{offset} #{table_name}.#{primary_key} #{rest} #{new_order}) #{order} "
      else
        new_sql = "#{select} TOP #{limit} #{rest_of_query} AND #{table_name}.#{primary_key} NOT IN (#{select} TOP #{offset} #{table_name}.#{primary_key} #{rest} #{new_order}) #{order} "
      end

      sql.replace(new_sql)
    end
  end
  sql
end