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On Rails Migrations Continued

Posted by Richard White Sat, 04 Feb 2006 02:06:00 GMT

Encountered another issue with migrations today when trying to do the following

add_column :appt_service_logins, :id, :primary_key

This threw an error when running rake migrate against my PostgreSQL DB that essentially boiled down to migrations trying to run the following SQL

ALTER TABLE appt_service_logins ADD id

Obviously missing the datatype for the column. I tracked this down to type_to_sql returning nil. This was because def native_database_types define a Hash where primary key does not map to another Hash with a :name key (see previous post). Therefore the following in def type_to_sql would return nil since it specifically looks for the value using the :name key.

def type_to_sql(type, limit = nil) #:nodoc:
  native = native_database_types[type]
  limit ||= native[:limit]
  column_type_sql = native[:name]
  column_type_sql << "(#{limit})" if limit
  column_type_sql  
end

To get around this I modified def type_to_sql to use the native value if column_type_sql was nil.

def type_to_sql(type, limit = nil) #:nodoc:
  native = native_database_types[type]
  limit ||= native[:limit] 
  column_type_sql = native[:name]
  column_type_sql << "(#{limit})" if limit      
  if column_type_sql
    column_type_sql
  else
    native
  end
end

I have no idea what the implications of such a change would be which is why I submitted this as a bug.

In the meantime since I was worried about the implications of changing def type_to_sql, I added a native database type of bigserial and am adding the column as a non-null bigserial and with a unique index.

Changes to postgre_extensions.rb:

def native_database_types
{
  :primary_key => "bigserial primary key",
  :string      => { :name => "character varying", :limit => 255 },
  :text        => { :name => "text" },
  :integer     => { :name => "integer" },
  :float       => { :name => "float" },
  :datetime    => { :name => "timestamp" },
  :timestamp   => { :name => "timestamp" },
  :time        => { :name => "time" },
  :date        => { :name => "date" },
  :binary      => { :name => "bytea" },
  :boolean     => { :name => "boolean" },
  :bigint      => { :name => "int8" },
  <strong>:bigserial   => { :name => "bigserial" }</strong>
}
end

In self.up in the migration file:

add_column :appt_service_logins, :id, :bigserial, :null => false
add_index :appt_service_logins, :id, :unique

To wrap up I attempted to put all of my changes into a Rails plugin so I wouldn’t have to put require ‘postgre_extensions’ at the top of each migration file as this fellow did but to no avail. I settled on just adding require ‘postgre_extensions’ to the bottom of my environment.rb. If you know of a better way to do this, let me know.