1. What exceptions are in logs?
2. For legacy databases you might find useful class methods set_primary_key, set_table_name, set_sequence_name, see
and primary_key_prefix_type http://dev.rubyonrails.org/browser/trunk/activerecord/lib/active_record/base.rb?rev=6139#L279
So, the problem shows out clear: you connect to database with postgres role that does not have enough privilieges. Make sure you did GRANT'ed necessary access to database objects.
Well, using legacy database schema that does not conform to Rails conventions and cannot be changed, is indeed not very DRY.
e.g. when defining associations one may need to declare foreign key
names and class names explicitly, but from my own experience it's not
that bad even with dozens of tables 
But, you can dig postgres system tables (I mean with some ruby/sql script) and build first scratch version of ActiveRecord models automatically.
Hi, for all those who may be wishing to integrate postgresql into their rails framework, I received this from the postgresql list:
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