= Schema Evolution Design =

== Introduction ==

A way to migrate database changes as a project evolves.

== Participants

Design: JoeTennies
Development:

== Status ==

* ~~Process started~~
* Design drafted
* Design proposed
* Design approved
* Implementation drafted
* Implementation proposed <put ticket number here>
* Ticket approved
* Released

== Objectives ==

Primary are required for first round of implementation. Secondary are things to be considered in the design but not required for first round of implementation.

=== Primary ===

* Store revision number of tables
* Store updates as python scripts
* Reverse migrations? (from version 6 to version 4)
* Modify database schemas (Will require updates to database API)
  * Add columns
  * Remove columns
  * Change table names
  * Change column lengths
  * Change column/table attributes
    * Unique


=== Secondary ===

* Allow personal patches against a database schema?
  * This would allow an individual to store customizations but still be able to do schema migrations
* Detect bad migrations
  * Detect that data may be lost

== Non-Goals ==

* Autodetection of changes
  * This should be left for external tools like South or nashvegas to do