To reproduce:

1. Create a postgresql table with a varchar primary key.
2. Specify a new key value and try to save the new record.

ActiveRecord will insert the record, and then immediately bomb with an 
error when it tries to query a non-existent sequence table.  This error 
causes the inserted record to get rolled back.

Looks like ActiveRecord assumes that all primary keys have a sequence 
table in postgresql.

Am I forgetting to do something or is this a major bug in ActiveRecord?