We create all database objects with scripts in the myfirstpackage/sql/ directory. All database scripts are database-specific and are thus in either the myfirstpackage/sql/oracle or myfirstpackage/sql/postgresql. Packages can support Oracle, PostgreSQL, or both. In this tutorial, we'll work only with PostgreSQL

The first file will be myfirstpackage-create.sql. The package manager requires a file with the name packagekey-create.sql, which it will run automatically when the package in installed. This file should create all tables and views.

Our package is going to store all of its information in one table. It takes more than just a CREATE TABLE command, however, because we want to integrate our table with the OpenACS system. By making each record in our table an OpenACS object, we gain access to the permissions system and to services that integrate with OpenACS objects, such as general-comments and notification. The cost that our table creation code must include several functions and stored procedures and is fairly complicated even for a simple table.

There are many kinds of OpenACS objects in the system. (You can see them with select object_type from acs_object_types;.) One such object is the content_item, which is part of the content repository system. We will make our data objects children of the content_item object. Not only will we gain the benefits of both OpenACS Objects and content objects, we can also use some content repository functions to simplify our database creation. (More information about ACS Objects. More information about the Content Repository.)

Figure 9.2. Tutorial Data Model

The top of each sql file has some standard comments, including doc tags such as @author which will be picked up by the API browser. The string $Id: tutorial-database.html,v 1.22 2004/02/27 11:20:52 joela Exp $ will automatically be expanded when the file is checked in to cvs.

[service0 ~]$ cd /var/lib/aolserver/service0/packages/myfirstpackage/sql/postgresql
[service0 postgresql]$ emacs myfirstpackage-create.sql

Paste this into the file and save and close.

-- creation script
--
-- @author joel@aufrecht.org
-- @cvs-id &Id:$
--

select content_type__create_type(
    'mfp_note',                    -- content_type
    'content_revision',            -- supertype
    'MFP Note',                    -- pretty_name,
    'MFP Notes',                   -- pretty_plural
    'mfp_notes',                   -- table_name
    'note_id',                     -- id_column
    null                           -- name_method
);

-- necessary to work around limitation of content repository:
select content_folder__register_content_type(-100,'mfp_note','t');

The creation script calls a function, content_type__create_type, which in turn creates the necessary database changes to support our data object. Notice the use of "mfp." This token, derived from "My First Package," ensures that our object is unlikely to conflict with objects from other packages.

Create a database file to drop everything if the package is uninstalled.

[service0 postgresql]$ emacs myfirstpackage-drop.sql

-- drop script
--
-- @author joel@aufrecht.org
-- @cvs-id &Id:$
--
select content_folder__unregister_content_type(-100,'mfp_note','t');

select content_type__drop_type(
	   'mfp_note',
	   't',
	   't'
    );

Run the create script manually to add your tables and functions.

[service0 postgresql]$ psql -f myfirstpackage-create.sql
psql:myfirstpackage-create.sql:15: NOTICE:  CREATE TABLE / PRIMARY KEY will create implicit index 'mfp_notes_pkey' for table 'mfp_notes'
psql:myfirstpackage-create.sql:15: NOTICE:  CREATE TABLE will create implicit trigger(s) for FOREIGN KEY check(s)
 content_type__create_type
---------------------------
                         0
(1 row)

 content_folder__register_content_type
---------------------------------------
                                     0
(1 row)

[service0 postgresql]$

If there are errors, use them to debug the sql file and try again. If there are errors in the database table creation, you may need to run the drop script to drop the table so that you can recreate it. The drop script will probably have errors since some of the things it's trying to drop may be missing. They can be ignored.

Once you get the same output as shown above, test the drop script:

[service0 postgresql]$ psql -f myfirstpackage-drop.sql
 content_folder__unregister_content_type
-----------------------------------------
                                       0
(1 row)

 content_type__drop_type
-------------------------
                       0
(1 row)

[service0 postgresql]$

Once both scripts are working without errors, run the create script one last time and proceed.

[service0 postgresql]$ psql -f myfirstpackage-create.sql