Under Construction This proposal is under construction and is not ready for review.

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Zend Framework: Zend_Db_Schema_Manager Component Proposal

Table of Contents

1. Overview

Zend_Db_Schema_Manager maintains a database schema as a set of PHP files in a database agnostic format.
This ensures that the same change can be applied to multiple databases and all changes can be stored in
a version control system.

2. References

• Rails: ActiveRecord::Migration
• Rails Migration Cheat Sheet

3. Component Requirements, Constraints, and Acceptance Criteria

• Zend_Db_Schema_Manager requires a database specific adapter for each supported database.

4. Dependencies on Other Framework Components

• Zend_Exception
• Zend_Db

5. Theory of Operation

Zend_Db_SchemaManager enables easy changes to a database schema without destroying
data. They can also be rolled back if required. The schema manager executes database
migration scripts which are collections of database operations such as adding a field to
a table.

Each migration script is a class extending from Zend_Db_Schema_Change which contains two
abstract methods: up() and down(). Migration script files are named like 001_initialSchema.php
so that they can be operated upon in order. The class within 001_initialSchema.php is called
initialSchema.

Note that for Zend_Db_Schema_Manager to work, a new table is required within the the database
being managed. This table, schema_info, holds the current version of the schema and is used
by the Manager to decide if the current operation is an upgrade or a rollback.

In order to work, a database independent structure to describe a table is used.

6. Milestones / Tasks

• Milestone 1: Completed design on wiki
• Milestone 2: Working prototype with unit tests checked into the incubator.
• Milestone 3: Documentation exists

7. Class Index

• Zend_Db_Schema_Exception - exception handler
• Zend_Db_Schema_Manager - class to manage migrating from one schema version to another
• Zend_Db_Schema_Change - abstract class to inherit each migrations script from
• Zend_Db_Schema_Table - database independant table creation and altering
• Zend_Db_Schema_Adapter - abstract class for database specific schema-change adapters
• Zend_Db_Schema_Adapter_Mysql - MySQL adapter for adding/deleting/editing tables
• Zend_Db_Schema_Adapter_Mssql - MSSQL adapter for adding/deleting/editing tables

8. Use Cases

The main use case is when you need to change the database schema of a live application.
Obviously this is done on the development machine first and the Schema_Manager will
ensure that the same changes to the database will occur on the live site.

Example migration script: 001_AddSecondEmailAddressColumn.php

Example CLI script to run the Manager: updateSchema.php

9. Class Skeletons