We create all database objects with scripts in the
myfirstpackage/sql/ directory. All database
scripts are database-specific and are thus in either the
directory. Packages can support Oracle, PostgreSQL, or both. In
this tutorial, we will be working 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
notification. The cost is that our table
creation code must include several functions, stored procedures,
and is complicated (even for simple tables).
There are many kinds of OpenACS objects in the system. (You can
see them with the psql code:
object_type from acs_object_types;.) One such object is the
content_item, which is part of the content repository system. To
use it, we will make our data objects children of the
content_revision object, which is a child of content_item. 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
The top of each SQL file has some standard comments, including
doc tags such as
will be picked up by the API browser. The string
$Id:$ will automatically be expanded when
the file is checked in to cvs.
cd /var/lib/aolserver/$OPENACS_SERVICE_NAME/packages/myfirstpackage/sql/postgresql[$OPENACS_SERVICE_NAME postgresql]$
Paste the text below into the file, save, and close.
Figure 9.3. The Database Creation Script
-- creation script -- -- @author email@example.com -- @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 in PL/pgSQL (PL/pgSQL is a
procedural language extension to sql),
content_type__create_type, which in turn
creates the necessary database changes to support our data object.
Notice the use of "mfp." This is derived from "My
First Package" and 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.
Figure 9.4. Database Deletion Script
-- drop script -- -- @author firstname.lastname@example.org -- @cvs-id &Id:$ -- select content_folder__unregister_content_type(-100,'mfp_note','t'); select content_type__drop_type( 'mfp_note', 't', 't' );
(like the creation script the drop script calls a PL/pgSQL
Run the create script manually to add your tables and functions.
psql service0 -f myfirstpackage-create.sqlpsql: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) [$OPENACS_SERVICE_NAME postgresql]$
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:
psql service0 -f myfirstpackage-drop.sqlcontent_type__drop_type ------------------------- 0 (1 row) [$OPENACS_SERVICE_NAME postgresql]$
Once both scripts are working without errors, run the create script one last time and proceed.
psql service0 -f myfirstpackage-create.sql