FOSS Project Spotlight: Appaserver

Tim Riley — Fri, 14 Dec 2018 13:00:00 +0000

An introduction to an application server that allows you to build MySQL user interfaces without programming.

Assume you are tasked to write a browser-based, MySQL user interface for the table called CITY. CITY has two columns. The column names are city_name and state_code—each combined are the primary key.

Your user interface must enable users to execute the four main SQL operations: select, insert, update and delete. The main characteristics for each operation are:

The select operation needs an HTML prompt form to request a query. It also needs a where clause generator to select from CITY. After forking MySQL and retrieving the raw rows, it needs to translate them into an HTML table form.
The HTML table form needs to be editable, and user edits need to be translated into update statements.
Each resulting row following the execution of a query is a candidate for deletion.
The insert operation needs a blank form. It also needs to translate Apache's common gateway interface (CGI) into insert statements.

So, you might create the source file called city.c and type in all the required code. Of course, relational databases have relations. One city has many persons residing in it. Assume the PERSON table has the column names of full_name, street_address, city_name and state_code. full_name and street_address combined are the primary key (Figure 1).

Figure 1. Database Schema of Many Persons Residing in One City

Are you going to create the source file called person.c too? What about customer.c, inventory.c, order.c, ...?

Alternatively, you might create the source files called select.c, insert.c, update.c and delete.c. Then each of these modules would need as input:

A single table name.
The table's additional attributes.
The table's column names and additional attributes.
A recursive list of related tables.
Apache's CGI dictionary output.

The principle behind Appaserver is this multi-module approach. Appaserver stores table names in a table. Each table's column names and relations are also stored in tables. Taking the table-driven concept to the nth degree forms a database of a database. You can glean a detailed understanding of how the Appaserver database is modeled from https://appahost.com/appaserver_database_schema.pdf.

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