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PostgREST tutorials

This tutorial is part of our PostgREST tutorial series:

PostgREST installation and setup

Disclaimer: This tutorial was developed on Mac OSX 10.14.6 and tested on Ubuntu 18.04. Windows compatibility cannot be guaranteed.

In this tutorial you'll learn how to install and setup PostgREST, the RESTful API framework for any existing PostgreSQL database.

Step 1 - Docker PostgreSQL & PostGIS setup

If you are willing to run PostgreSQL via Docker we recommend to use Kartoza's docker recipe which comes bundled with PostGIS as an extension.

We will keep it simple and guide you through this tutorial using this image but the general steps are almost identical for a host installation.

Create your Docker Postgres container named postgrest_tut on port 5432 (or whichever port you prefer).

sudo docker run --name "postgrest_tut" -p 5432:5432 -e POSTGRES_MULTIPLE_EXTENSIONS=postgis -d -t kartoza/postgis

You will have to configure Postgres to make sure it trusts connections (this is merely for the tutorial and shouldn't be used in production this way).

sudo docker exec -it postgrest_tut bash

Inside the container first of all install an editor, e.g. nano, and then navigate to the folder where the Postgres config lives.

apt-get update && apt-get install nano

# this could also be a different version and depends on your installation
cd /etc/postgresql/12/main/

In pg_hba.conf you will have to make a small change to the settings under Database administrative login by Unix domain socket from peer to trust. On lines 84 & 85, it should look like this:

# Database administrative login by Unix domain socket
local   all             postgres                                trust

Then restart the Docker container and bring up the psql prompt:

sudo docker restart postgrest_tut
sudo docker exec -it postgrest_tut psql -U postgres

Within the prompt you will have to enable the PostGIS extension with:

postgres=# CREATE EXTENSION postgis;
postgres=# \q

In some tutorials we make use of the raster2pgsql utility provided by PostGIS. However, that's not available in Kartoza's Docker image and only available in the PostGIS apt-get package. So you'll have to install it manually inside the Docker container:

sudo docker exec -it postgrest_tut bash -c "apt-get update && apt-get install postgis"

Step 2 - PostgREST installation

To keep it simple, we suggest you follow the installation instructions on postgrest.org which will depend on your operating system.

Once everything is installed you will be able to simply run PostgREST with:

postgrest

And if everything is working correctly it will print out its version and information about configuration.

Step 3 - Create API Schema

Postgrest will require its own API schema, so bring up the psql prompt of our Docker container again (alternatively psql -U postgres if it's running on your host OS).

sudo docker exec -it postgrest_tut psql -U postgres

psql (9.6.3)
Type "help" for help.

postgres=#

Create an arbitrarily named schema for your database objects which will be exposed via the PostgREST API. Execute the following SQL statements inside the psql prompt:

CREATE SCHEMA api;

Next, you should add a role to use for anonymous web requests. When a request hits the API, PostgREST will switch into this database role to run the queries.

CREATE ROLE web_anon NOLOGIN;

GRANT USAGE ON SCHEMA api TO web_anon;

Now, the web_anon role has permission to access functions in the API schema.

As the authors of PostgREST point out, it's actually good practice to create a dedicated role for connecting to the database, instead of using the highly privileged postgres role. To do that, name the role authenticator and also grant this user the ability to switch to the web_anon role:

CREATE ROLE authenticator NOINHERIT LOGIN PASSWORD 'gisops';
GRANT web_anon TO authenticator;

We'll regularly use the World Robinson's EPSG:54030 projection to make sure we use a suitable projection for our spatial calculations. However, PostGIS misses that projections in its CRS table, so please add it to your database:

INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext) values ( 54030, 'ESRI', 54030, '+proj=robin +lon_0=0 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs ', 'PROJCS["World_Robinson",GEOGCS["GCS_WGS_1984",DATUM["WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Robinson"],PARAMETER["False_Easting",0],PARAMETER["False_Northing",0],PARAMETER["Central_Meridian",0],UNIT["Meter",1],AUTHORITY["EPSG","54030"]]');

PostgREST requires a configuration file to specify the database connection. Go ahead and create a file named gisops-tutorial.conf with the following information (remember to adapt the port and password if you have changed it in the earlier steps).

db-uri = "postgres://authenticator:gisops@localhost:5432/postgres"
db-schema = "api"
db-anon-role = "web_anon"
server-port = 3000

Now we are ready to start PostgREST.

postgrest gisops-tutorial.conf
# or ./postgrest gisops-tutorial.conf

You should be able to see something like this:

Listening on port 3000
Attempting to connect to the database...
Connection successful

The PostgREST server is now ready to serve web requests.

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