==============
Gadfly Backend
==============

This document outlines the design and implementation of the Gadfly (relational
database) backend.


About Gadfly
============

Gadfly  is  a  collection  of  python modules that provides relational
database  functionality  entirely implemented in Python. It supports a
subset  of  the intergalactic standard RDBMS Structured Query Language
SQL.


Basic Structure
===============

Roundup supports a dynamic schema, something which doesn't map very well to a
relational database table schema (or at least, it's frowned upon :)

Approaches:

1. Map roundup classes to relational tables. Automatically detect schema
   changes and modify the gadfly table schemas appropriately. Multilinks
   (which represent a many-to-many relationship) are handled through
   intermediate tables.
   Journals are stored adjunct to the per-class tables.
2. Map roundup classes to relational tables. Automatically detect schema
   changes and modify the gadfly table schemas appropriately. Multilinks
   are handled with string representations of the id lists.
   Journals are stored adjunct to the per-class tables.
3. Four tables:

   - classes: class id, name
   - properties: class id, property id, name, type, options
   - nodes: class id, node id, property id, value  (one row per multilink value)
   - journals: class id, node id, event, description

   The classes and properties tables will need to be kept in sync with the
   roundup schema.
4. Two less efficient tables:

   - nodes: class, property, node id, value    (one row per multilink value)
   - journals: class, node id, event, description

   The classes and properties tables will need to be kept in sync with the
   roundup schema.