Module: Randumb::ActiveRecord::Relation

Included in:
ActiveRecord::Relation
Defined in:
lib/randumb/relation.rb

Instance Method Summary collapse

Instance Method Details

#random(max_items = nil) ⇒ Object

If the max_items argument is omitted, one random entity will be returned. If you provide the integer argument, you will get back an array of records.



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# File 'lib/randumb/relation.rb', line 12

def random(max_items = nil)
  random_weighted(nil, max_items)
end

#random_by_id_shuffle(max_items = nil) ⇒ Object

This was my first implementation, adding it as an option for people to use and to fall back on for pesky DB one off situations…

https://github.com/spilliton/randumb/issues/7



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# File 'lib/randumb/relation.rb', line 48

def random_by_id_shuffle(max_items = nil)
  return_first_record = max_items.nil? # see return switch at end
  max_items ||= 1
  relation = clone
  ids = fetch_random_ids(relation, max_items)

  # build new scope for final query
  the_scope = klass.includes(includes_values)

  # specifying empty selects caused bug in rails 3.0.0/3.0.1
  the_scope = the_scope.select(select_values) unless select_values.empty?

  # get the records and shuffle since the order of the ids
  # passed to find_all_by_id isn't retained in the result set
  records = the_scope.find_all_by_id(ids).shuffle!

  # return first record if method was called without parameters
  return_first_record ? records.first : records
end

#random_weighted(ranking_column, max_items = nil) ⇒ Object

If ranking_column is provided, that named column wil be multiplied by a random number to determine probability of order. The ranking column must be numeric.



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# File 'lib/randumb/relation.rb', line 18

def random_weighted(ranking_column, max_items = nil)
  relation = clone
  return random_by_id_shuffle(max_items) if is_randumb_postges_case?(relation, ranking_column)
  raise_unless_valid_ranking_column(ranking_column)
  # get clause for current db type
  order_clause = random_order_clause(ranking_column)

  the_scope = if ::ActiveRecord::VERSION::MAJOR == 3 && ::ActiveRecord::VERSION::MINOR < 2
    # AR 3.0.0 support
    relation.order(order_clause)
  else
    # keep prior orders and append random
    all_orders = (relation.orders + [order_clause]).join(", ")
    # override all previous orders
    relation.reorder(all_orders) 
  end
  
  # override the limit if they are requesting multiple records
  if max_items && (!relation.limit_value || relation.limit_value > max_items)
    the_scope = the_scope.limit(max_items)
  end

  # return first record if method was called without parameters
  max_items ? the_scope.to_a : the_scope.first
end