City of Helsinki nature database and API (LTJ)

LTJ is a backend service for storing and retrieving data about important natural sites and observations thereof. This information is structured along the form of a database developed in the City of Helsinki during several years. It is not particularly specific to Helsinki and should be usable elsewhere as well.

Data in LTJ is accessed throught its REST-like API. In addition there is a reasonably functional admnistration site implemented using Django admin. In case you are not familiar with Django admin, it is a simple forms based editor of Web 1.0 style.

LTJ also has support for displaying HTML-formatted reports for natural sites. These are designed for linking from the Helsinki map service (kartta.hel.fi).

Installation

This applies to both development and simple production scale (nature information is, sadly, not very popular). Note that you won't need to follow this approach if you have your own favorite Python process.

Prerequisites

Python 3
PostgreSQL with PostGIS (other databases are not tested at all)

Configuration

LTJ uses environment variables for its configuration. These are particularly nice in container environments or other managed environments (like Heroku).

However for development, setting the environment variables is a bit annoying. In this case you will want to create config.env in the root of the source (ie. same place as this README). Start by renaming config.env.example to config.env. The example file should contain every setting currently available and commonly used values thereof.

Preparing the database

LTJ uses PostGIS for storing the geometries (areas on map) and/or points (locations on map) of natural phenomena. Therefore you need to have the PostGIS extension installed and enable for the database.

Begin by adding enabling PostGIS extension for the default template;

sudo -u postgres psql -d template1 -c "CREATE EXTENSION IF NOT EXISTS postgis;"

Create user and database

sudo -u postgres createuser -P -R -S ltj  # use password `ltj`
sudo -u postgres createdb -O ltj ltj

Allow user to create test database

sudo -u postgres psql -c "ALTER USER ltj CREATEDB;"

The application is build based on existing database, import data from a dump ( note that it should be fresh dump from original database without any migration being applied on nature model):

psql -h localhost -p 5432 -U ltj ltj < data_dump.sql

Run the utility script to fix the database so that it can be managed by django:

psql -h localhost -U ltj -d ltj -a -f utility/add_alter_columns.sql
psql -h localhost -U ltj -d ltj -a -f utility/add_id_seq.sql
psql -h localhost -U ltj -d ltj -a -f utility/protection_level_comments.sql  # optional

# convert columns with type `timestamp without time zone` to type `timestamp with time zone`
psql -h localhost -U ltj -d ltj -a -f utility/drop_views.sql -f utility/tz_aware_timestamps.sql -f utility/create_views.sql

Fake initial when first time run migrations on nature app:

python manage.py migrate nature --fake-initial

If migrations change the columns that are used by views, drop views before applying migrations and recreate after it.

psql -h localhost -U ltj -d ltj -a -f utility/drop_views.sql
python manage.py migrate
psql -h localhost -U ltj -d ltj -a -f utility/create_views.sql

Tests

Run tests

py.test

Run tests with coverage report

py.test --cov-report html --cov .

Open htmlcov/index.html for the coverage report.

Translations

To compile the Finnish translations run

python manage.py compilemessages

City-of-Helsinki / ltj