config/initializers/postgresql_adapter.rb

   1 module ActiveRecord
   2   module ConnectionAdapters
   3     class PostgreSQLAdapter
   4       alias_method :old_pk_and_sequence_for, :pk_and_sequence_for
   5
   6       def pk_and_sequence_for(table)
   7         result = query(<<-end_sql, 'PK and serial sequence')[0]
   8           SELECT attr.attname, seq.relname
   9           FROM pg_class      seq,
  10                pg_attribute  attr,
  11                pg_depend     dep,
  12                pg_namespace  name,
  13                pg_constraint cons
  14           WHERE seq.oid           = dep.objid
  15             AND seq.relkind       = 'S'
  16             AND attr.attrelid     = dep.refobjid
  17             AND attr.attnum       = dep.refobjsubid
  18             AND attr.attrelid     = cons.conrelid
  19             AND attr.attnum       = cons.conkey[1]
  20             AND cons.contype      = 'p'
  21             AND dep.classid       = '"pg_class"'::regclass
  22             AND dep.refclassid    = '"pg_class"'::regclass
  23             AND dep.refobjid      = '#{quote_table_name(table)}'::regclass
  24         end_sql
  25
  26         if result.nil? or result.empty?
  27           old_pk_and_sequence_for(table)
  28         else
  29           [result.first, result.last]
  30         end
  31       end
  32     end
  33   end
  34 end