What’s schemadoc?

The schemadoc gem includes a ready-to-use command line tool named - surprise, surprise - schemadoc that lets you auto-generate your database schema documentation for tables, columns, and more.

Overview. The schemadoc tool connects to your database (e.g. SQLite, PostgreSQL, etc.) and writes out the schema info in database.json

{
  "schemas": [
    {
      "name": "football",
      "tables": [
        {
          "name": "alltime_standing_entries",
          "columns": [
            {
              "name": "id",
              "type": "integer",
              "default": null,
              "null": false
            },
            {
              "name": "alltime_standing_id",
              "type": "integer",
              "default": null,
              "null": false
            },
            {
              "name": "team_id",
              "type": "integer",
              "default": null,
              "null": false
            },
...

and also builds an A-Z symbols index stored in symbols.json.

{
    "name": "A",
    "tables": [
      "alltime_standing_entries",
      "alltime_standings",
      "assocs",
      "assocs_assocs"
    ],
    "columns": [
      {
        "name": "abbr",
        "tables": [
          "regions"
        ]
      },
      {
        "name": "address",
        "tables": [
          "grounds",
          "teams"
        ]
      },
...

Drop the JSON documents in the _data/ folder for your static site theme (template pack) and let Jekyll (or GitHub Pages) do the rest.

Examples in the real world. See the football.db or beer.db for live examples.

Getting Started w/ schemadoc

Let’s document the football.db SQLite version in three steps:

  • Step 1: Let’s create the football.db
  • Step 2: Let’s write out the schema info in JSON
  • Step 3: Let’s generate a static schema documentation site

Step 1: Let’s create the football.db

First let’s create the football.db itself. Pull in the sportdb-models gem and use the built-in “auto-migrate” method SportDb.create_all that will create all database tables. Example:

mkfootball.rb:

require 'logger'
require 'sportdb/models'      # use $ gem install sportdb-models

DB_CONFIG = {
  adapter: 'sqlite3',
  database: './football.db'
}

ActiveRecord::Base.logger = Logger.new( STDOUT )
ActiveRecord::Base.establish_connection( DB_CONFIG )

SportDb.create_all

puts 'Done.'

Run the script:

$ ruby ./makfootball.rb

Now you’ve got an empty football.db with many many tables. Let’s document the database schema(ta).

Step 2: Let’s write out the schema info in JSON

The schemadoc command line tool requires a configuration file, that is, /schemadoc.yml that lists the connection settings and the schemas (such as football, world, and the works.) Example:

schemadoc.yml:

## connection spec

database:
  adapter:  sqlite3
  database: ./football.db


## main tables

football:
  name: Football

## world tables

world:
  name: World
  tables:
    - continents
    - countries
    - regions
    - cities
    - places
    - names
    - langs
    - usages
    
## works tables

works:
  name: The Works
  tables:
     - logs
     - props
     - tags
     - taggings

Now run the schemadoc tool:

$ ./schemadoc

and you will end-up with two JSON files, that is, database.json and symbols.json.

Step 3: Let’s generate a static schema documentation site

Get a copy of the book-templates/schema static site theme and drop (copy) the two JSON files, that is, database.json and symbols.json into the _data/ folder. Change the site settings in _config.yml and run:

$ ./jekyll build

That’s it. Open up in your browser the ./_site/index.html page. Enjoy your databasse schema documentation.

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