class ActiveRecord::ConnectionAdapters::PostgreSQLAdapter

def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)

Executes an INSERT query and returns the new record's ID
def insert(sql, name = nil, pk = nil, id_value = nil, sequence_name = nil)
  # Extract the table from the insert sql. Yuck.
  table = sql.split(" ", 4)[2].gsub('"', '')
  # Try an insert with 'returning id' if available (PG >= 8.2)
  if supports_insert_with_returning?
    pk, sequence_name = *pk_and_sequence_for(table) unless pk
    if pk
      id = select_value("#{sql} RETURNING #{quote_column_name(pk)}")
      clear_query_cache
      return id
    end
  end
  # Otherwise, insert then grab last_insert_id.
  if insert_id = super
    insert_id
  else
    # If neither pk nor sequence name is given, look them up.
    unless pk || sequence_name
      pk, sequence_name = *pk_and_sequence_for(table)
    end
    # If a pk is given, fallback to default sequence name.
    # Don't fetch last insert id for a table without a pk.
    if pk && sequence_name ||= default_sequence_name(table, pk)
      last_insert_id(table, sequence_name)
    end
  end
end