Creating Tables in DrProject

Posted 2007-01-18

Courtesy of David Scannell, here’s a quick rundown of how to create a new table in DrProject’s database. (Yes, I know, we should convert to SQLObject or SQLAlchemy; if you have time to do the work, please let me know…)

Suppose I want to create a table called Demo with three fields:

Named: string
ID: integer (primary key)
TicketID: Integer (foreign key)

We’ll assume that all work is being done in a drproject/demo directory, that you have init.py set up, and you have modified setup.py file to recognize the new package.

Step 1: Create the Model

A. Create a file call model.py.

B. Import the following:

from drproject.db.record import *         # Base for all database modelling

from drproject.ticket.model import Ticket # Because we want a foreign key

C. Create a new subclass for record.

Class Demo(Record):

D. Associated this model with a database table (by default the table it gets associated with is the same as the name of the class):

Class Demo(Record):   _table='demo_table'

E. Now add the columns to the table:

Class Demo(Record):

_table='demo_table'

id = IdColumn()                # Creates a self-incrementing id

name = TextColumn()            # String column

ticket_id = ForeignKey(Ticket) # Makes this a foreign key to the Ticket Table

F. Make the ID column our primary key:

Class Demo(Record):

_table='demo_table'

id = IdColumn()

name = TextColumn()

ticket_id = ForeignKey(Ticket)

_key = (id,)

Done.

Step 2: Create the System

A. Create a file called api.py.

B. Import the following:

from drproject.core import *

from drproject.env import EnvironmentSetupParticipant # For database creation

from drproject.demo.model import *                    # Our database model

C. Create our EnviromentSetupParticipant subclass.

Class DemoSystem(EnvironmentSetupParticipant):

D. Associate the table that this new system will work with. In our case, it is the demo table.

Class DemoSystem(EnvironmentSetupParticipant):

database_tables = (Demo,)

E. Give our system a name and version number:

Class DemoSystem(EnvironmentSetupParticipant):

database_tables = (Demo,)

version_propery = 'demo_system'

version = 1

Done.

Step 3: Finishing Off

Now, when we create a new environment, DrProject will go over all the EnvironmentSetupParticipant objects, and create all the database tables each one is associated with. Process occurs in the method init of the class Environment in the file drproject/env.py.