Added region sequencing of primary keys for Postgres.

Skip setting sequence on a table create if the value is 0 since it will start the first value at 1 anyway.
This fixes the PG error 'setval: value 0 is out of bounds for sequence vms_id_seq...' encountered when migrating a new DB.

BugzID: 15452,9772,13475,16850

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

@@ -293,6 +293,27 @@ module ActiveRecord
           result.rows.first.first
         end
 
+        # Sets the sequence of a table's primary key to the specified value.
+        def set_pk_sequence!(table, value, pk = nil, sequence = nil) #:nodoc:
+          unless pk and sequence
+            default_pk, default_sequence = pk_and_sequence_for(table)
+            pk ||= default_pk
+            sequence ||= default_sequence
+          end
+
+          if pk
+            if sequence
+              quoted_sequence = quote_column_name(sequence)
+
+              select_value <<-end_sql, 'SCHEMA'
+              SELECT setval('#{quoted_sequence}', #{value})
+              end_sql
+            else
+              @logger.warn "#{table} has primary key #{pk} with no default sequence" if @logger
+            end
+          end
+        end
+
         # Resets the sequence of a table's primary key to the maximum value.
         def reset_pk_sequence!(table, pk = nil, sequence = nil) #:nodoc:
           unless pk and sequence